diff --git a/.cspell.json b/.cspell.json
index b72ea55deb2..6b2e04fec4d 100644
--- a/.cspell.json
+++ b/.cspell.json
@@ -64,6 +64,9 @@
     "ALLOC",
     "ISOE",
     "isoe",
+    "authscheme",
+    "Vistor",
+    "eventstreaming",
     // AWS general
     "Arns",
     "AMZN",
@@ -77,6 +80,9 @@
     "AWSSTL",
     "reparsed",
     "reparses",
+    "MRAP",
+    "ISOF",
+    "isof",
     // AWS Signature
     "SIGV",
     "AUTHV",
diff --git a/src/aws-cpp-sdk-core/include/smithy/client/features/ChunkingInterceptor.h b/src/aws-cpp-sdk-core/include/smithy/client/features/ChunkingInterceptor.h
index 2ed637db883..0b377593fb8 100644
--- a/src/aws-cpp-sdk-core/include/smithy/client/features/ChunkingInterceptor.h
+++ b/src/aws-cpp-sdk-core/include/smithy/client/features/ChunkingInterceptor.h
@@ -156,9 +156,41 @@ class ChunkingInterceptor : public smithy::interceptor::Interceptor {
     ~ChunkingInterceptor() override = default;
 
     ModifyRequestOutcome ModifyBeforeSigning(smithy::interceptor::InterceptorContext& context) override {
+      auto request = context.GetTransmitRequest();
+
+      if (!ShouldApplyChunking(request, context)) {
+        return request;
+      }
+
+      const auto& hashPair = request->GetRequestHash();
+      if (hashPair.second != nullptr) {
+        Aws::String checksumHeaderValue = Aws::String(CHECKSUM_HEADER_PREFIX) + hashPair.first;
+        request->DeleteHeader(checksumHeaderValue.c_str());
+        request->SetHeaderValue(Aws::Http::AWS_TRAILER_HEADER, checksumHeaderValue);
+        request->SetTransferEncoding(Aws::Http::CHUNKED_VALUE);
+
+        if (!request->HasContentEncoding()) {
+          request->SetContentEncoding(Aws::Http::AWS_CHUNKED_VALUE);
+        } else {
+          Aws::String currentEncoding = request->GetContentEncoding();
+          if (currentEncoding.find(Aws::Http::AWS_CHUNKED_VALUE) == Aws::String::npos) {
+            request->SetContentEncoding(Aws::String{Aws::Http::AWS_CHUNKED_VALUE} + "," + currentEncoding);
+          }
+        }
+
+        if (request->HasHeader(Aws::Http::CONTENT_LENGTH_HEADER)) {
+          request->SetHeaderValue(Aws::Http::DECODED_CONTENT_LENGTH_HEADER, request->GetHeaderValue(Aws::Http::CONTENT_LENGTH_HEADER));
+          request->DeleteHeader(Aws::Http::CONTENT_LENGTH_HEADER);
+        }
+      }
+
+      return context.GetTransmitRequest();
+    }
+
+    ModifyRequestOutcome ModifyBeforeTransmit(smithy::interceptor::InterceptorContext& context) override {
         auto request = context.GetTransmitRequest();
 
-        if (!ShouldApplyChunking(request)) {
+        if (!ShouldApplyChunking(request, context)) {
             return request;
         }
 
@@ -167,29 +199,6 @@ class ChunkingInterceptor : public smithy::interceptor::Interceptor {
             return request;
         }
 
-        // Set up chunked encoding headers for checksum calculation
-        const auto& hashPair = request->GetRequestHash();
-        if (hashPair.second != nullptr) {
-            Aws::String checksumHeaderValue = Aws::String(CHECKSUM_HEADER_PREFIX) + hashPair.first;
-            request->DeleteHeader(checksumHeaderValue.c_str());
-            request->SetHeaderValue(Aws::Http::AWS_TRAILER_HEADER, checksumHeaderValue);
-            request->SetTransferEncoding(Aws::Http::CHUNKED_VALUE);
-            
-            if (!request->HasContentEncoding()) {
-                request->SetContentEncoding(Aws::Http::AWS_CHUNKED_VALUE);
-            } else {
-                Aws::String currentEncoding = request->GetContentEncoding();
-                if (currentEncoding.find(Aws::Http::AWS_CHUNKED_VALUE) == Aws::String::npos) {
-                    request->SetContentEncoding(Aws::String{Aws::Http::AWS_CHUNKED_VALUE} + "," + currentEncoding);
-                }
-            }
-
-            if (request->HasHeader(Aws::Http::CONTENT_LENGTH_HEADER)) {
-                request->SetHeaderValue(Aws::Http::DECODED_CONTENT_LENGTH_HEADER, request->GetHeaderValue(Aws::Http::CONTENT_LENGTH_HEADER));
-                request->DeleteHeader(Aws::Http::CONTENT_LENGTH_HEADER);
-            }
-        }
-
         auto chunkedBody = Aws::MakeShared<AwsChunkedIOStream>(
             ALLOCATION_TAG, request.get(), originalBody);
 
@@ -202,7 +211,13 @@ class ChunkingInterceptor : public smithy::interceptor::Interceptor {
     }
 
 private:
-    bool ShouldApplyChunking(const std::shared_ptr<Aws::Http::HttpRequest>& request) const {
+    bool ShouldApplyChunking(const std::shared_ptr<Aws::Http::HttpRequest>& request,
+                             const smithy::interceptor::InterceptorContext& context) const {
+        //TODO: remove this once we figure out why MRAP cannot trail chunk
+        const auto signerName = context.GetAttribute("signer_name");
+        if (signerName.has_value() && signerName.value() == "AsymmetricSignatureV4") {
+            return false;
+        }
         // Use configuration setting to determine chunking behavior
         if (m_httpClientChunkedMode != Aws::Client::HttpClientChunkedMode::DEFAULT) {
             return false;
diff --git a/src/aws-cpp-sdk-core/include/smithy/interceptor/Interceptor.h b/src/aws-cpp-sdk-core/include/smithy/interceptor/Interceptor.h
index b133857624b..e9de73150c1 100644
--- a/src/aws-cpp-sdk-core/include/smithy/interceptor/Interceptor.h
+++ b/src/aws-cpp-sdk-core/include/smithy/interceptor/Interceptor.h
@@ -16,6 +16,7 @@ namespace smithy
 
             using ModifyRequestOutcome = Aws::Utils::Outcome<std::shared_ptr<Aws::Http::HttpRequest>, Aws::Client::AWSError<Aws::Client::CoreErrors>>;
             virtual ModifyRequestOutcome ModifyBeforeSigning(InterceptorContext& context) = 0;
+            virtual ModifyRequestOutcome ModifyBeforeTransmit(InterceptorContext& context) { return context.GetTransmitRequest(); }
 
             using ModifyResponseOutcome = Aws::Utils::Outcome<std::shared_ptr<Aws::Http::HttpResponse>, Aws::Client::AWSError<Aws::Client::CoreErrors>>;
             virtual ModifyResponseOutcome ModifyBeforeDeserialization(InterceptorContext& context) = 0;
diff --git a/src/aws-cpp-sdk-core/include/smithy/interceptor/InterceptorContext.h b/src/aws-cpp-sdk-core/include/smithy/interceptor/InterceptorContext.h
index 08cfc836f37..03c96e89558 100644
--- a/src/aws-cpp-sdk-core/include/smithy/interceptor/InterceptorContext.h
+++ b/src/aws-cpp-sdk-core/include/smithy/interceptor/InterceptorContext.h
@@ -9,6 +9,7 @@
 #include <aws/core/http/HttpRequest.h>
 #include <aws/core/http/HttpResponse.h>
 #include <aws/core/client/CoreErrors.h>
+#include <aws/crt/Optional.h>
 
 namespace smithy
 {
@@ -53,9 +54,12 @@ namespace smithy
                 m_transmitResponse = transmitResponse;
             }
 
-            Aws::String GetAttribute(const Aws::String& key) const
-            {
-                return m_attributes.at(key);
+            Aws::Crt::Optional<Aws::String> GetAttribute(const Aws::String& key) const {
+              const auto attribute = m_attributes.find(key);
+              if (attribute == m_attributes.end()) {
+                return {};
+              }
+              return attribute->second;
             }
 
             void SetAttribute(const Aws::String& key, const Aws::String& value)
diff --git a/src/aws-cpp-sdk-core/source/client/AWSClient.cpp b/src/aws-cpp-sdk-core/source/client/AWSClient.cpp
index 90f83a58f33..4dbc7895352 100644
--- a/src/aws-cpp-sdk-core/source/client/AWSClient.cpp
+++ b/src/aws-cpp-sdk-core/source/client/AWSClient.cpp
@@ -570,6 +570,7 @@ HttpResponseOutcome AWSClient::AttemptOneRequest(const std::shared_ptr<Aws::Http
 
     InterceptorContext context{request};
     context.SetTransmitRequest(httpRequest);
+    context.SetAttribute("signer_name", signerName);
     for (const auto& interceptor : m_interceptors)
     {
         const auto modifiedRequest = interceptor->ModifyBeforeSigning(context);
@@ -597,6 +598,13 @@ HttpResponseOutcome AWSClient::AttemptOneRequest(const std::shared_ptr<Aws::Http
         request.GetRequestSignedHandler()(*httpRequest);
     }
 
+    for (const auto& interceptor : m_interceptors) {
+      const auto modifiedRequest = interceptor->ModifyBeforeTransmit(context);
+      if (!modifiedRequest.IsSuccess()) {
+        return modifiedRequest.GetError();
+      }
+    }
+
     AWS_LOGSTREAM_DEBUG(AWS_CLIENT_LOG_TAG, "Request Successfully signed");
     auto httpResponse = TracingUtils::MakeCallWithTiming<std::shared_ptr<HttpResponse>>(
         [&]() -> std::shared_ptr<HttpResponse> {
diff --git a/src/aws-cpp-sdk-core/source/smithy/client/AwsSmithyClientBase.cpp b/src/aws-cpp-sdk-core/source/smithy/client/AwsSmithyClientBase.cpp
index 34f33336d36..f185bfacc74 100644
--- a/src/aws-cpp-sdk-core/source/smithy/client/AwsSmithyClientBase.cpp
+++ b/src/aws-cpp-sdk-core/source/smithy/client/AwsSmithyClientBase.cpp
@@ -426,6 +426,19 @@ void AwsSmithyClientBase::AttemptOneRequestAsync(std::shared_ptr<AwsSmithyClient
         HandleAsyncReply(std::move(pRequestCtx), std::move(pResponse));
     };
 
+    for (const auto& interceptor : m_interceptors)
+    {
+      auto modifiedRequest = interceptor->ModifyBeforeTransmit(*pRequestCtx->m_interceptorContext);
+      if (!modifiedRequest.IsSuccess())
+      {
+        pExecutor->Submit([modifiedRequest, responseHandler]() mutable
+          {
+              responseHandler(modifiedRequest.GetError());
+          });
+        return;
+      }
+    }
+
     // TODO: async http client
 #if 0
     AWS_LOGSTREAM_DEBUG(AWS_SMITHY_CLIENT_LOG, "Request Successfully signed");