diff --git a/generated/src/aws-cpp-sdk-dynamodb/include/aws/dynamodb/DynamoDBClientConfiguration.h b/generated/src/aws-cpp-sdk-dynamodb/include/aws/dynamodb/DynamoDBClientConfiguration.h
index d8586dde26c..49f5a9a449b 100644
--- a/generated/src/aws-cpp-sdk-dynamodb/include/aws/dynamodb/DynamoDBClientConfiguration.h
+++ b/generated/src/aws-cpp-sdk-dynamodb/include/aws/dynamodb/DynamoDBClientConfiguration.h
@@ -21,17 +21,13 @@ namespace Aws
 
             DynamoDBClientConfiguration(const DynamoDBClientConfiguration& other)
                 : Aws::Client::GenericClientConfiguration(other),
-                  enableEndpointDiscovery(BaseClientConfigClass::enableEndpointDiscovery),
-                  accountId{other.accountId},
-                  accountIdEndpointMode{other.accountIdEndpointMode}
+                  enableEndpointDiscovery(BaseClientConfigClass::enableEndpointDiscovery)
             {
             }
 
             DynamoDBClientConfiguration(DynamoDBClientConfiguration&& other) noexcept
                 : Aws::Client::GenericClientConfiguration(std::move(other)),
-                  enableEndpointDiscovery(BaseClientConfigClass::enableEndpointDiscovery),
-                  accountId{std::move(other.accountId)},
-                  accountIdEndpointMode{std::move(other.accountIdEndpointMode)}
+                  enableEndpointDiscovery(BaseClientConfigClass::enableEndpointDiscovery)
             {
             }
 
@@ -40,8 +36,6 @@ namespace Aws
                 if (this == &other)
                     return *this;
                 Aws::Client::GenericClientConfiguration::operator =(other);
-                accountId = other.accountId;
-                accountIdEndpointMode = other.accountIdEndpointMode;
                 return *this;
             }
 
@@ -50,8 +44,6 @@ namespace Aws
                 if (this == &other)
                     return *this;
                 Aws::Client::GenericClientConfiguration::operator =(std::move(other));
-                accountId = std::move(other.accountId);
-                accountIdEndpointMode = std::move(other.accountIdEndpointMode);
                 return *this;
             }
 
@@ -90,14 +82,6 @@ namespace Aws
              */
             Aws::Crt::Optional<bool>& enableEndpointDiscovery;
 
-            /**
-             * The AWS AccountId used for the request.
-             */
-            Aws::String accountId;
-            /**
-             * The AccountId Endpoint Mode.
-             */
-            Aws::String accountIdEndpointMode = "preferred";
         private:
             void LoadDynamoDBSpecificConfig(const Aws::String& profileName);
         };
diff --git a/generated/src/aws-cpp-sdk-dynamodb/source/DynamoDBClientConfiguration.cpp b/generated/src/aws-cpp-sdk-dynamodb/source/DynamoDBClientConfiguration.cpp
index 353bfeb192c..709bcc0fe68 100644
--- a/generated/src/aws-cpp-sdk-dynamodb/source/DynamoDBClientConfiguration.cpp
+++ b/generated/src/aws-cpp-sdk-dynamodb/source/DynamoDBClientConfiguration.cpp
@@ -45,15 +45,6 @@ void DynamoDBClientConfiguration::LoadDynamoDBSpecificConfig(const Aws::String&
   if(!enableEndpointDiscovery) {
     enableEndpointDiscovery = IsEndpointDiscoveryEnabled(this->endpointOverride, inputProfileName);
   }
-  // accountId is intentionally not set here: AWS_ACCOUNT_ID env variable may not match the provided credentials.
-  // it must be set by an auth provider / identity resolver or by an SDK user.
-  static const char AWS_ACCOUNT_ID_ENDPOINT_MODE_ENVIRONMENT_VARIABLE[] = "AWS_ACCOUNT_ID_ENDPOINT_MODE";
-  static const char AWS_ACCOUNT_ID_ENDPOINT_MODE_CONFIG_FILE_OPTION[] = "account_id_endpoint_mode";
-  accountIdEndpointMode = ClientConfiguration::LoadConfigFromEnvOrProfile(AWS_ACCOUNT_ID_ENDPOINT_MODE_ENVIRONMENT_VARIABLE,
-                                                                               inputProfileName,
-                                                                               AWS_ACCOUNT_ID_ENDPOINT_MODE_CONFIG_FILE_OPTION,
-                                                                               {"required", "disabled", "preferred"}, /* allowed values */
-                                                                               "preferred" /* default value */);
 }
 
 DynamoDBClientConfiguration::DynamoDBClientConfiguration(const Client::ClientConfigurationInitValues &configuration)
diff --git a/generated/src/aws-cpp-sdk-s3control/include/aws/s3control/S3ControlClientConfiguration.h b/generated/src/aws-cpp-sdk-s3control/include/aws/s3control/S3ControlClientConfiguration.h
index 73bb1e63557..fcb0c09b58f 100644
--- a/generated/src/aws-cpp-sdk-s3control/include/aws/s3control/S3ControlClientConfiguration.h
+++ b/generated/src/aws-cpp-sdk-s3control/include/aws/s3control/S3ControlClientConfiguration.h
@@ -18,36 +18,6 @@ namespace Aws
         {
             using BaseClientConfigClass = Aws::Client::GenericClientConfiguration;
 
-            S3ControlClientConfiguration(const S3ControlClientConfiguration& other)
-                : Aws::Client::GenericClientConfiguration(other),
-                  accountId{other.accountId}
-            {
-            }
-
-            S3ControlClientConfiguration(S3ControlClientConfiguration&& other) noexcept
-                : Aws::Client::GenericClientConfiguration(std::move(other)),
-                  accountId{std::move(other.accountId)}
-            {
-            }
-
-            S3ControlClientConfiguration& operator=(const S3ControlClientConfiguration& other)
-            {
-                if (this == &other)
-                    return *this;
-                Aws::Client::GenericClientConfiguration::operator =(other);
-                accountId = other.accountId;
-                return *this;
-            }
-
-            S3ControlClientConfiguration& operator=(S3ControlClientConfiguration&& other) noexcept
-            {
-                if (this == &other)
-                    return *this;
-                Aws::Client::GenericClientConfiguration::operator =(std::move(other));
-                accountId = std::move(other.accountId);
-                return *this;
-            }
-
             S3ControlClientConfiguration(const Client::ClientConfigurationInitValues &configuration = {});
 
             /**
@@ -72,10 +42,6 @@ namespace Aws
             S3ControlClientConfiguration(const Client::ClientConfiguration& config);
             bool useArnRegion = false;
             Client::AWSAuthV4Signer::PayloadSigningPolicy payloadSigningPolicy = Client::AWSAuthV4Signer::PayloadSigningPolicy::RequestDependent;
-            /**
-             * The Account ID used to send the request. This is an optional parameter that will be set automatically for operations that require it.
-             */
-            Aws::String accountId;
         private:
             void LoadS3ControlSpecificConfig(const Aws::String& profileName);
         };
diff --git a/generated/src/aws-cpp-sdk-s3control/source/S3ControlClientConfiguration.cpp b/generated/src/aws-cpp-sdk-s3control/source/S3ControlClientConfiguration.cpp
index 9289b07fa28..d34c1a61354 100644
--- a/generated/src/aws-cpp-sdk-s3control/source/S3ControlClientConfiguration.cpp
+++ b/generated/src/aws-cpp-sdk-s3control/source/S3ControlClientConfiguration.cpp
@@ -24,8 +24,6 @@ void S3ControlClientConfiguration::LoadS3ControlSpecificConfig(const Aws::String
   {
     useArnRegion = true;
   }
-  // accountId is intentionally not set here: AWS_ACCOUNT_ID env variable may not match the provided credentials.
-  // it must be set by an auth provider / identity resolver or by an SDK user.
 }
 
 S3ControlClientConfiguration::S3ControlClientConfiguration(const Client::ClientConfigurationInitValues &configuration)
diff --git a/src/aws-cpp-sdk-core/include/aws/core/client/ClientConfiguration.h b/src/aws-cpp-sdk-core/include/aws/core/client/ClientConfiguration.h
index 13e5458da7b..9b0fd8de6a2 100644
--- a/src/aws-cpp-sdk-core/include/aws/core/client/ClientConfiguration.h
+++ b/src/aws-cpp-sdk-core/include/aws/core/client/ClientConfiguration.h
@@ -465,6 +465,16 @@ namespace Aws
                */
               bool useAnonymousAuth = false;
             } winHTTPOptions;
+
+          /**
+            * The AWS AccountId used for the request.
+            */
+          Aws::String accountId;
+
+          /**
+           * The AccountId Endpoint Mode.
+           */
+          Aws::String accountIdEndpointMode = "preferred";
         };
 
         /**
diff --git a/src/aws-cpp-sdk-core/include/aws/core/client/UserAgent.h b/src/aws-cpp-sdk-core/include/aws/core/client/UserAgent.h
index 70e83c178cb..81f630b7dfb 100644
--- a/src/aws-cpp-sdk-core/include/aws/core/client/UserAgent.h
+++ b/src/aws-cpp-sdk-core/include/aws/core/client/UserAgent.h
@@ -26,6 +26,10 @@ enum class UserAgentFeature {
   FLEXIBLE_CHECKSUMS_REQ_WHEN_REQUIRED,
   FLEXIBLE_CHECKSUMS_RES_WHEN_SUPPORTED,
   FLEXIBLE_CHECKSUMS_RES_WHEN_REQUIRED,
+  ACCOUNT_ID_MODE_PREFERRED,
+  ACCOUNT_ID_MODE_DISABLED,
+  ACCOUNT_ID_MODE_REQUIRED,
+  RESOLVED_ACCOUNT_ID,
 };
 
 class AWS_CORE_API UserAgent {
diff --git a/src/aws-cpp-sdk-core/include/smithy/client/AwsSmithyClient.h b/src/aws-cpp-sdk-core/include/smithy/client/AwsSmithyClient.h
index 5be45b494fc..ced88664d14 100644
--- a/src/aws-cpp-sdk-core/include/smithy/client/AwsSmithyClient.h
+++ b/src/aws-cpp-sdk-core/include/smithy/client/AwsSmithyClient.h
@@ -346,32 +346,20 @@ namespace client
             ResponseT,
             ErrorMarshallerT>>;
 
-        /**
-         * SFINAE implementation for refreshing client context params enabled if the client configuration
-         * type has a AccountId member. If there is a corresponding member we want to use that in the endpoint
-         * calculation and set it as a client context parameter.
-         */
-        template <typename T, typename = void>
-        struct HasAccountId : std::false_type {};
-
-        template<typename T>
-        struct HasAccountId<T, decltype(void(std::declval<T>().accountId))> : std::true_type {};
-
-        template<typename ConfigT = ServiceClientConfigurationT, typename std::enable_if<HasAccountId<ConfigT>::value, int>::type = 0>
         GetContextEndpointParametersOutcome GetContextEndpointParametersImpl(const AwsSmithyClientAsyncRequestContext& ctx) const {
           Aws::Vector<Aws::Endpoint::EndpointParameter> endpointParameters;
           const auto resolvedAccountId = ctx.m_awsIdentity->accountId();
-          if (resolvedAccountId.has_value() && !resolvedAccountId.value().empty() && m_clientConfiguration.accountId.empty()) {
+          const auto resolvedNonEmptyAccountId = resolvedAccountId.has_value() && !resolvedAccountId.value().empty();
+          // Set user agent if account ID was resolved in identity provider
+          if (resolvedNonEmptyAccountId) {
+            ctx.m_pRequest->AddUserAgentFeature(Aws::Client::UserAgentFeature::RESOLVED_ACCOUNT_ID);
+          }
+          // Only set EP param if client configuration does not have a configured account ID and we resolved a account id
+          if (resolvedNonEmptyAccountId && m_clientConfiguration.accountId.empty()) {
             endpointParameters.emplace_back("AccountId", resolvedAccountId.value(), Aws::Endpoint::EndpointParameter::ParameterOrigin::OPERATION_CONTEXT);
           }
           return endpointParameters;
         }
-
-        template<typename ConfigT = ServiceClientConfigurationT, typename std::enable_if<!HasAccountId<ConfigT>::value, int>::type = 0>
-        GetContextEndpointParametersOutcome GetContextEndpointParametersImpl(const AwsSmithyClientAsyncRequestContext& ctx) const {
-          AWS_UNREFERENCED_PARAM(ctx);
-          return Aws::Vector<Aws::Endpoint::EndpointParameter>{};
-        }
     };
 
 } // namespace client
diff --git a/src/aws-cpp-sdk-core/source/client/ClientConfiguration.cpp b/src/aws-cpp-sdk-core/source/client/ClientConfiguration.cpp
index 784c4c8b70a..4e114b1bd21 100644
--- a/src/aws-cpp-sdk-core/source/client/ClientConfiguration.cpp
+++ b/src/aws-cpp-sdk-core/source/client/ClientConfiguration.cpp
@@ -39,6 +39,8 @@ static const char* REQUEST_MIN_COMPRESSION_SIZE_BYTES_CONFIG_VAR = "request_min_
 static const char* AWS_EXECUTION_ENV = "AWS_EXECUTION_ENV";
 static const char* DISABLE_IMDSV1_CONFIG_VAR = "AWS_EC2_METADATA_V1_DISABLED";
 static const char* DISABLE_IMDSV1_ENV_VAR = "ec2_metadata_v1_disabled";
+static const char* AWS_ACCOUNT_ID_ENDPOINT_MODE_ENVIRONMENT_VARIABLE = "AWS_ACCOUNT_ID_ENDPOINT_MODE";
+static const char* AWS_ACCOUNT_ID_ENDPOINT_MODE_CONFIG_FILE_OPTION = "account_id_endpoint_mode";
 
 using RequestChecksumConfigurationEnumMapping = std::pair<const char*, RequestChecksumCalculation>;
 static const std::array<RequestChecksumConfigurationEnumMapping, 2> REQUEST_CHECKSUM_CONFIG_MAPPING = {{
@@ -278,12 +280,21 @@ void setConfigFromEnvOrProfile(ClientConfiguration &config)
     if (disableIMDSv1 == "true") {
         config.disableImdsV1 = true;
     }
+
+    // accountId is intentionally not set here: AWS_ACCOUNT_ID env variable may not match the provided credentials.
+    // it must be set by an auth provider / identity resolver or by an SDK user.
+    config.accountIdEndpointMode = ClientConfiguration::LoadConfigFromEnvOrProfile(AWS_ACCOUNT_ID_ENDPOINT_MODE_ENVIRONMENT_VARIABLE,
+        config.profileName,
+        AWS_ACCOUNT_ID_ENDPOINT_MODE_CONFIG_FILE_OPTION,
+        {"required", "disabled", "preferred"}, /* allowed values */
+        "preferred" /* default value */);
 }
 
 ClientConfiguration::ClientConfiguration()
 {
     this->disableIMDS = false;
     setLegacyClientConfigurationParameters(*this);
+    setConfigFromEnvOrProfile(*this);;
 
     if (!this->disableIMDS &&
         region.empty() &&
@@ -300,13 +311,13 @@ ClientConfiguration::ClientConfiguration()
         return;
     }
     region = Aws::String(Aws::Region::US_EAST_1);
-    setConfigFromEnvOrProfile(*this);
 }
 
 ClientConfiguration::ClientConfiguration(const ClientConfigurationInitValues &configuration)
 {
     this->disableIMDS = configuration.shouldDisableIMDS;
     setLegacyClientConfigurationParameters(*this);
+    setConfigFromEnvOrProfile(*this);
 
     if (!this->disableIMDS &&
         region.empty() &&
@@ -323,7 +334,6 @@ ClientConfiguration::ClientConfiguration(const ClientConfigurationInitValues &co
         return;
     }
     region = Aws::String(Aws::Region::US_EAST_1);
-    setConfigFromEnvOrProfile(*this);
 }
 
 ClientConfiguration::ClientConfiguration(const char* profile, bool shouldDisableIMDS)
@@ -333,6 +343,7 @@ ClientConfiguration::ClientConfiguration(const char* profile, bool shouldDisable
         this->profileName = Aws::String(profile);
     }
     setLegacyClientConfigurationParameters(*this);
+    setConfigFromEnvOrProfile(*this);
     // Call EC2 Instance Metadata service only once
     Aws::String ec2MetadataRegion;
     bool hasEc2MetadataRegion = false;
@@ -368,13 +379,13 @@ ClientConfiguration::ClientConfiguration(const char* profile, bool shouldDisable
     }
 
     AWS_LOGSTREAM_WARN(CLIENT_CONFIG_TAG, "User specified profile: [" << profile << "] is not found, will use the SDK resolved one.");
-    setConfigFromEnvOrProfile(*this);
 }
 
 ClientConfiguration::ClientConfiguration(bool /*useSmartDefaults*/, const char* defaultMode, bool shouldDisableIMDS)
 {
     this->disableIMDS = shouldDisableIMDS;
     setLegacyClientConfigurationParameters(*this);
+    setConfigFromEnvOrProfile(*this);
 
     // Call EC2 Instance Metadata service only once
     Aws::String ec2MetadataRegion;
@@ -397,7 +408,6 @@ ClientConfiguration::ClientConfiguration(bool /*useSmartDefaults*/, const char*
     }
 
     Aws::Config::Defaults::SetSmartDefaultsConfigurationParameters(*this, defaultMode, hasEc2MetadataRegion, ec2MetadataRegion);
-    setConfigFromEnvOrProfile(*this);
 }
 
 std::shared_ptr<RetryStrategy> InitRetryStrategy(Aws::String retryMode)
diff --git a/src/aws-cpp-sdk-core/source/client/UserAgent.cpp b/src/aws-cpp-sdk-core/source/client/UserAgent.cpp
index f0cc5adc08c..694eab676c6 100644
--- a/src/aws-cpp-sdk-core/source/client/UserAgent.cpp
+++ b/src/aws-cpp-sdk-core/source/client/UserAgent.cpp
@@ -9,7 +9,9 @@
 #include <aws/core/utils/logging/LogMacros.h>
 #include <aws/core/utils/memory/stl/AWSStringStream.h>
 #include <aws/crt/Config.h>
+#include <aws/crt/Optional.h>
 
+#include <iterator>
 #include <numeric>
 #include <utility>
 
@@ -33,7 +35,11 @@ const std::pair<UserAgentFeature, const char*> BUSINESS_METRIC_MAPPING[] = {
     {UserAgentFeature::FLEXIBLE_CHECKSUMS_REQ_WHEN_SUPPORTED, "Z"},
     {UserAgentFeature::FLEXIBLE_CHECKSUMS_REQ_WHEN_REQUIRED, "a"},
     {UserAgentFeature::FLEXIBLE_CHECKSUMS_RES_WHEN_SUPPORTED, "b"},
-    {UserAgentFeature::FLEXIBLE_CHECKSUMS_RES_WHEN_REQUIRED, "c"}
+    {UserAgentFeature::FLEXIBLE_CHECKSUMS_RES_WHEN_REQUIRED, "c"},
+    {UserAgentFeature::ACCOUNT_ID_MODE_PREFERRED, "P"},
+    {UserAgentFeature::ACCOUNT_ID_MODE_DISABLED , "Q"},
+    {UserAgentFeature::ACCOUNT_ID_MODE_REQUIRED, "R"},
+    {UserAgentFeature::RESOLVED_ACCOUNT_ID, "T"},
 };
 
 Aws::String BusinessMetricForFeature(UserAgentFeature feature) {
@@ -53,6 +59,22 @@ const std::pair<const char*, UserAgentFeature> RETRY_FEATURE_MAPPING[] = {
     {"adaptive", UserAgentFeature::RETRY_MODE_ADAPTIVE},
 };
 
+const std::pair<const char*, UserAgentFeature> ACCOUNT_ID_MODE_MAPPING[] = {
+    {"preferred", UserAgentFeature::ACCOUNT_ID_MODE_PREFERRED},
+    {"disabled", UserAgentFeature::ACCOUNT_ID_MODE_DISABLED},
+    {"required", UserAgentFeature::ACCOUNT_ID_MODE_REQUIRED},
+};
+
+Aws::Crt::Optional<UserAgentFeature> BusinessMetricForAccountIdMode(const Aws::String& accountIdMode) {
+  const auto *const accountIdFeature = std::find_if(std::begin(ACCOUNT_ID_MODE_MAPPING),
+    std::end(ACCOUNT_ID_MODE_MAPPING),
+    [&accountIdMode](const std::pair<const char*, UserAgentFeature>& mapping) -> bool { return mapping.first == accountIdMode; });
+  if (accountIdFeature == std::end(ACCOUNT_ID_MODE_MAPPING)) {
+    return {};
+  }
+  return accountIdFeature->second;
+}
+
 const char* EXEC_ENV_VAR = "AWS_EXECUTION_ENV";
 const char* METADATA = "md";
 const char* METADATA_DELIMINATOR = "/";
@@ -94,6 +116,10 @@ UserAgent::UserAgent(const ClientConfiguration& clientConfiguration,
 #undef XSTR
 #endif
 {
+  const auto accountIdMode = BusinessMetricForAccountIdMode(clientConfiguration.accountIdEndpointMode);
+  if (accountIdMode.has_value()) {
+    m_features.emplace(accountIdMode.value());
+  }
 }
 
 Aws::String UserAgent::SerializeWithFeatures(const Aws::Set<UserAgentFeature>& features) const {
diff --git a/tests/aws-cpp-sdk-dynamodb-unit-tests/DynamoDBUnitTests.cpp b/tests/aws-cpp-sdk-dynamodb-unit-tests/DynamoDBUnitTests.cpp
index 705fd85148b..4419ed1c0ce 100644
--- a/tests/aws-cpp-sdk-dynamodb-unit-tests/DynamoDBUnitTests.cpp
+++ b/tests/aws-cpp-sdk-dynamodb-unit-tests/DynamoDBUnitTests.cpp
@@ -21,6 +21,7 @@
 #include <aws/testing/mocks/aws/auth/MockAWSHttpResourceClient.h>
 #include <aws/testing/mocks/http/MockHttpClient.h>
 #include <aws/testing/platform/PlatformTesting.h>
+#include <aws/testing/utils/UserAgentUtils.h>
 #include <gtest/gtest.h>
 
 #include <memory>
@@ -449,6 +450,12 @@ TEST_F(DynamoDBUnitTest, ShouldUseStandardEndpointIfAccountIdMissingFromCredenti
   EXPECT_TRUE(listTablesOutcome.IsSuccess());
   const auto requestSeen = mock_http_client_->GetMostRecentHttpRequest();
   EXPECT_EQ("https://dynamodb.us-east-1.amazonaws.com", requestSeen.GetUri().GetURIString());
+  const auto features = GetFeaturesForRequest(requestSeen);
+  EXPECT_TRUE(!features.empty());
+  // AccountId is disabled
+  EXPECT_TRUE(std::find(features.begin(), features.end(), "P") != features.end());
+  // Identity resolved a accountId
+  EXPECT_TRUE(std::find(features.begin(), features.end(), "T") == features.end());
 }
 
 
@@ -487,6 +494,12 @@ TEST_F(DynamoDBUnitTest, ShouldUseAccountIDEndpointFromCredentialsFile)
   EXPECT_TRUE(listTablesOutcome.IsSuccess());
   const auto requestSeen = mock_http_client_->GetMostRecentHttpRequest();
   EXPECT_EQ("https://spike-spiegel.ddb.us-east-1.amazonaws.com", requestSeen.GetUri().GetURIString());
+  const auto features = GetFeaturesForRequest(requestSeen);
+  EXPECT_TRUE(!features.empty());
+  // AccountId is disabled
+  EXPECT_TRUE(std::find(features.begin(), features.end(), "P") != features.end());
+  // Identity resolved a accountId
+  EXPECT_TRUE(std::find(features.begin(), features.end(), "T") != features.end());
 }
 
 TEST_F(DynamoDBUnitTest, ShouldUseAccountIDEndpointFromEnviornmentCredentialsProvider)
@@ -521,6 +534,12 @@ TEST_F(DynamoDBUnitTest, ShouldUseAccountIDEndpointFromEnviornmentCredentialsPro
   EXPECT_TRUE(listTablesOutcome.IsSuccess());
   const auto requestSeen = mock_http_client_->GetMostRecentHttpRequest();
   EXPECT_EQ("https://ein.ddb.us-east-1.amazonaws.com", requestSeen.GetUri().GetURIString());
+  const auto features = GetFeaturesForRequest(requestSeen);
+  EXPECT_TRUE(!features.empty());
+  // AccountId is disabled
+  EXPECT_TRUE(std::find(features.begin(), features.end(), "P") != features.end());
+  // Identity resolved a accountId
+  EXPECT_TRUE(std::find(features.begin(), features.end(), "T") != features.end());
 }
 
 TEST_F(DynamoDBUnitTest, ShouldUseAccountIDEndpointFromProcessCredentialsProvider)
@@ -555,6 +574,12 @@ TEST_F(DynamoDBUnitTest, ShouldUseAccountIDEndpointFromProcessCredentialsProvide
   EXPECT_TRUE(listTablesOutcome.IsSuccess());
   const auto requestSeen = mock_http_client_->GetMostRecentHttpRequest();
   EXPECT_EQ("https://faye.ddb.us-east-1.amazonaws.com", requestSeen.GetUri().GetURIString());
+  const auto features = GetFeaturesForRequest(requestSeen);
+  EXPECT_TRUE(!features.empty());
+  // AccountId is disabled
+  EXPECT_TRUE(std::find(features.begin(), features.end(), "P") != features.end());
+  // Identity resolved a accountId
+  EXPECT_TRUE(std::find(features.begin(), features.end(), "T") != features.end());
 }
 
 TEST_F(DynamoDBUnitTest, ShouldUseAccountIDEndpointFromSTSCredentialsProvider)
@@ -606,6 +631,12 @@ TEST_F(DynamoDBUnitTest, ShouldUseAccountIDEndpointFromSTSCredentialsProvider)
   EXPECT_TRUE(listTablesOutcome.IsSuccess());
   const auto requestSeen = mock_http_client_->GetMostRecentHttpRequest();
   EXPECT_EQ("https://rocco.ddb.us-east-1.amazonaws.com", requestSeen.GetUri().GetURIString());
+  const auto features = GetFeaturesForRequest(requestSeen);
+  EXPECT_TRUE(!features.empty());
+  // AccountId is disabled
+  EXPECT_TRUE(std::find(features.begin(), features.end(), "P") != features.end());
+  // Identity resolved a accountId
+  EXPECT_TRUE(std::find(features.begin(), features.end(), "T") != features.end());
 }
 
 TEST_F(DynamoDBUnitTest, ShouldUseAccountIDEndpointFromSSOCredentialsProvider)
@@ -672,6 +703,12 @@ TEST_F(DynamoDBUnitTest, ShouldUseAccountIDEndpointFromSSOCredentialsProvider)
   EXPECT_TRUE(listTablesOutcome.IsSuccess());
   const auto requestSeen = mock_http_client_->GetMostRecentHttpRequest();
   EXPECT_EQ("https://jet.ddb.us-east-1.amazonaws.com", requestSeen.GetUri().GetURIString());
+  const auto features = GetFeaturesForRequest(requestSeen);
+  EXPECT_TRUE(!features.empty());
+  // AccountId is disabled
+  EXPECT_TRUE(std::find(features.begin(), features.end(), "P") != features.end());
+  // Identity resolved a accountId
+  EXPECT_TRUE(std::find(features.begin(), features.end(), "T") != features.end());
 }
 
 TEST_F(DynamoDBUnitTest, ShouldUseAccountIDEndpointFromContainerCredentialsProvider)
@@ -704,6 +741,12 @@ TEST_F(DynamoDBUnitTest, ShouldUseAccountIDEndpointFromContainerCredentialsProvi
   EXPECT_TRUE(listTablesOutcome.IsSuccess());
   const auto requestSeen = mock_http_client_->GetMostRecentHttpRequest();
   EXPECT_EQ("https://Vicious.ddb.us-east-1.amazonaws.com", requestSeen.GetUri().GetURIString());
+  const auto features = GetFeaturesForRequest(requestSeen);
+  EXPECT_TRUE(!features.empty());
+  // AccountId is disabled
+  EXPECT_TRUE(std::find(features.begin(), features.end(), "P") != features.end());
+  // Identity resolved a accountId
+  EXPECT_TRUE(std::find(features.begin(), features.end(), "T") != features.end());
 }
 
 TEST_F(DynamoDBUnitTest, ShouldNotUseAccountIDEndpointWhenDisabled)
@@ -739,4 +782,84 @@ TEST_F(DynamoDBUnitTest, ShouldNotUseAccountIDEndpointWhenDisabled)
   EXPECT_TRUE(listTablesOutcome.IsSuccess());
   const auto requestSeen = mock_http_client_->GetMostRecentHttpRequest();
   EXPECT_EQ("https://dynamodb.us-east-1.amazonaws.com", requestSeen.GetUri().GetURIString());
+  const auto features = GetFeaturesForRequest(requestSeen);
+  EXPECT_TRUE(!features.empty());
+  // AccountId is disabled
+  EXPECT_TRUE(std::find(features.begin(), features.end(), "Q") != features.end());
+  // Identity resolved a accountId
+  EXPECT_TRUE(std::find(features.begin(), features.end(), "T") != features.end());
+}
+
+TEST_F(DynamoDBUnitTest, ShouldWorkWhenNoAccountIDAndRequired)
+{
+  // create enviornment variables with account id
+  const Environment::EnvironmentRAII environmentVariables{
+          {
+            {"AWS_ACCESS_KEY_ID", "the"},
+            {"AWS_SECRET_ACCESS_KEY", "real"},
+            {"AWS_SESSION_TOKEN", "folk"},
+          }};
+
+  DynamoDBClientConfiguration configuration;
+  configuration.region = "us-east-1";
+  configuration.accountIdEndpointMode = "required";
+
+  auto credsProvider = Aws::MakeShared<EnvironmentAWSCredentialsProvider>(LOG_TAG);
+
+  const auto accountIdClient = Aws::MakeShared<DynamoDBClient>(LOG_TAG, std::move(credsProvider), nullptr, configuration);
+
+  // mock response
+  auto successStream = Aws::MakeShared<StandardHttpRequest>(LOG_TAG, "cowboy.bebop/planets", HttpMethod::HTTP_GET);
+  successStream->SetResponseStreamFactory([]() -> IOStream* {
+    auto listTablesString =  R"({"LastEvaluatedTableName": "Planets","TableNames": ["Planets"]}))";
+    return Aws::New<StringStream>(LOG_TAG, listTablesString, std::ios_base::in | std::ios_base::binary);
+  });
+  auto successResponse = Aws::MakeShared<StandardHttpResponse>(LOG_TAG, successStream);
+  successResponse->SetResponseCode(HttpResponseCode::OK);
+
+  mock_http_client_->AddResponseToReturn(successResponse);
+  const auto listTablesOutcome = accountIdClient->ListTables();
+  EXPECT_TRUE(!listTablesOutcome.IsSuccess());
+  EXPECT_EQ(listTablesOutcome.GetError().GetMessage(), "AccountIdEndpointMode is required but no AccountID was provided or able to be loaded");
+}
+
+TEST_F(DynamoDBUnitTest, ShouldFailWhenNoAccountIDAndRequired)
+{
+  // create enviornment variables with account id
+  const Environment::EnvironmentRAII environmentVariables{
+            {
+              {"AWS_ACCESS_KEY_ID", "the"},
+              {"AWS_SECRET_ACCESS_KEY", "real"},
+              {"AWS_SESSION_TOKEN", "folk"},
+              {"AWS_ACCOUNT_ID", "blues"},
+            }};
+
+  DynamoDBClientConfiguration configuration;
+  configuration.region = "us-east-1";
+  configuration.accountIdEndpointMode = "required";
+
+  auto credsProvider = Aws::MakeShared<EnvironmentAWSCredentialsProvider>(LOG_TAG);
+
+  const auto accountIdClient = Aws::MakeShared<DynamoDBClient>(LOG_TAG, std::move(credsProvider), nullptr, configuration);
+
+  // mock response
+  auto successStream = Aws::MakeShared<StandardHttpRequest>(LOG_TAG, "cowboy.bebop/planets", HttpMethod::HTTP_GET);
+  successStream->SetResponseStreamFactory([]() -> IOStream* {
+    auto listTablesString =  R"({"LastEvaluatedTableName": "Planets","TableNames": ["Planets"]}))";
+    return Aws::New<StringStream>(LOG_TAG, listTablesString, std::ios_base::in | std::ios_base::binary);
+  });
+  auto successResponse = Aws::MakeShared<StandardHttpResponse>(LOG_TAG, successStream);
+  successResponse->SetResponseCode(HttpResponseCode::OK);
+
+  mock_http_client_->AddResponseToReturn(successResponse);
+  const auto listTablesOutcome = accountIdClient->ListTables();
+  EXPECT_TRUE(listTablesOutcome.IsSuccess());
+  const auto requestSeen = mock_http_client_->GetMostRecentHttpRequest();
+  EXPECT_EQ("https://blues.ddb.us-east-1.amazonaws.com", requestSeen.GetUri().GetURIString());
+  const auto features = GetFeaturesForRequest(requestSeen);
+  EXPECT_TRUE(!features.empty());
+  // AccountId is disabled
+  EXPECT_TRUE(std::find(features.begin(), features.end(), "R") != features.end());
+  // Identity resolved a accountId
+  EXPECT_TRUE(std::find(features.begin(), features.end(), "T") != features.end());
 }
\ No newline at end of file
diff --git a/tests/testing-resources/CMakeLists.txt b/tests/testing-resources/CMakeLists.txt
index 0711dd14a8d..59bd8345072 100644
--- a/tests/testing-resources/CMakeLists.txt
+++ b/tests/testing-resources/CMakeLists.txt
@@ -19,6 +19,7 @@ file(GLOB AWS_TESTING_HTTP_MOCKS_HEADERS "include/aws/testing/mocks/http/*.h")
 file(GLOB AWS_TESTING_CLIENT_MOCKS_HEADERS "include/aws/testing/mocks/aws/client/*.h")
 file(GLOB AWS_TESTING_MONITORING_MOCKS_HEADERS "include/aws/testing/mocks/monitoring/*.h")
 file(GLOB AWS_TESTING_PLATFORM_HEADERS "include/aws/testing/platform/*.h")
+file(GLOB AWS_TESTING_UTILS_HEADERS "include/aws/testing/utils/*.h")
 
 file(GLOB AWS_TESTING_SOURCE "source/*.cpp")
 file(GLOB AWS_TESTING_EXTERNAL_SOURCE "source/external/*.cc")
@@ -36,6 +37,7 @@ file(GLOB TestingResources_SHARED_SRC
     ${AWS_TESTING_CLIENT_MOCKS_HEADERS}
     ${AWS_TESTING_MONITORING_MOCKS_HEADERS}
     ${AWS_TESTING_PLATFORM_HEADERS}
+    ${AWS_TESTING_UTILS_HEADERS}
     ${AWS_TESTING_SOURCE}
     ${AWS_TESTING_EXTERNAL_SOURCE}
     ${AWS_TESTING_GTEST_SOURCE}
@@ -59,6 +61,7 @@ if(PLATFORM_WINDOWS)
     if(MSVC)
         source_group("Header Files\\aws\\testing" FILES ${AWS_TESTING_HEADERS})
         source_group("Header Files\\aws\\testing\\platform" FILES ${AWS_TESTING_PLATFORM_HEADERS})
+        source_group("Header Files\\aws\\testing\\utils" FILES ${AWS_TESTING_UTILS_HEADERS})
         source_group("Header Files\\aws\\external" FILES ${AWS_TESTING_EXTERNAL_HEADERS})
         source_group("Header Files\\aws\\external\\gtest" FILES ${AWS_TESTING_GTEST_HEADERS})
         source_group("Header Files\\aws\\external\\gtest\\internal" FILES ${AWS_TESTING_GTEST_HEADERS_INTERNAL})
@@ -148,6 +151,7 @@ install (FILES ${AWS_TESTING_GTEST_HEADERS} DESTINATION ${INCLUDE_DIRECTORY}/aws
 install (FILES ${AWS_TESTING_GTEST_HEADERS_INTERNAL} DESTINATION ${INCLUDE_DIRECTORY}/aws/external/gtest/internal)
 install (FILES ${AWS_TESTING_GTEST_HEADERS_INTERNAL_CUSTOM} DESTINATION ${INCLUDE_DIRECTORY}/aws/external/gtest/internal/custom)
 install (FILES ${AWS_TESTING_PLATFORM_HEADERS} DESTINATION ${INCLUDE_DIRECTORY}/aws/testing/platform)
+install (FILES ${AWS_TESTING_UTILS_HEADERS} DESTINATION ${INCLUDE_DIRECTORY}/aws/testing/utils)
 install (FILES ${AWS_TESTING_AUTH_MOCKS_HEADERS} DESTINATION ${INCLUDE_DIRECTORY}/aws/testing/mocks/aws/auth)
 install (FILES ${AWS_TESTING_CLIENT_MOCKS_HEADERS} DESTINATION ${INCLUDE_DIRECTORY}/aws/testing/mocks/aws/client)
 install (FILES ${AWS_TESTING_EVENT_MOCKS_HEADERS} DESTINATION ${INCLUDE_DIRECTORY}/aws/testing/mocks/event)
diff --git a/tests/testing-resources/include/aws/testing/utils/UserAgentUtils.h b/tests/testing-resources/include/aws/testing/utils/UserAgentUtils.h
new file mode 100644
index 00000000000..4bcdb2b617e
--- /dev/null
+++ b/tests/testing-resources/include/aws/testing/utils/UserAgentUtils.h
@@ -0,0 +1,26 @@
+/**
+  * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0.
+ */
+
+#pragma once
+#include <aws/core/client/UserAgent.h>
+#include <aws/core/http/HttpRequest.h>
+
+#include <gtest/gtest.h>
+
+inline Aws::Vector<Aws::String> GetFeaturesForRequest(const Aws::Http::HttpRequest &request) {
+  const auto& userAgentString = request.GetHeaderValue(Aws::Http::USER_AGENT_HEADER);
+  EXPECT_TRUE(!userAgentString.empty());
+  const auto userAgentValues = Aws::Utils::StringUtils::Split(userAgentString, ' ');
+  const Aws::String businessValuePrefix{"m/"};
+  auto businessMetrics = std::find_if(
+      userAgentValues.begin(), userAgentValues.end(),
+      [&businessValuePrefix](const Aws::String& value) -> bool { return value.find(businessValuePrefix) != Aws::String::npos; });
+  EXPECT_TRUE(businessMetrics != userAgentValues.end());
+  const auto metrics = [](Aws::String str, const Aws::String& sub) -> Aws::String {
+    str.replace(str.find(sub), sub.length(), "");
+    return str;
+  }(*businessMetrics, businessValuePrefix);
+  return Aws::Utils::StringUtils::Split(metrics, ',');
+}
\ No newline at end of file
diff --git a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/common/ServiceClientConfigurationHeader.vm b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/common/ServiceClientConfigurationHeader.vm
index 2ef845cb29e..16d0f153ee6 100644
--- a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/common/ServiceClientConfigurationHeader.vm
+++ b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/common/ServiceClientConfigurationHeader.vm
@@ -58,18 +58,6 @@ namespace ${rootNamespace}
 #set($addArgDummy = $copyCtorStatements.add("enableEndpointDiscovery(BaseClientConfigClass::enableEndpointDiscovery)"))
 #set($addArgDummy = $moveCtorStatements.add("enableEndpointDiscovery(BaseClientConfigClass::enableEndpointDiscovery)"))
 #end
-#if($serviceModel.endpointRuleSetModel.parameters.containsKey("AccountId"))
-#set($addArgDummy = $copyCtorStatements.add("accountId{other.accountId}"))
-#set($addArgDummy = $moveCtorStatements.add("accountId{std::move(other.accountId)}"))
-#set($addArgDummy = $copyAssignmentStatements.add("accountId = other.accountId;"))
-#set($addArgDummy = $moveAssignemntStatements.add("accountId = std::move(other.accountId);"))
-#end
-#if($serviceModel.endpointRuleSetModel.parameters.containsKey("AccountIdEndpointMode"))
-#set($addArgDummy = $copyCtorStatements.add("accountIdEndpointMode{other.accountIdEndpointMode}"))
-#set($addArgDummy = $moveCtorStatements.add("accountIdEndpointMode{std::move(other.accountIdEndpointMode)}"))
-#set($addArgDummy = $copyAssignmentStatements.add("accountIdEndpointMode = other.accountIdEndpointMode;"))
-#set($addArgDummy = $moveAssignemntStatements.add("accountIdEndpointMode = std::move(other.accountIdEndpointMode);"))
-#end
 #if(!$copyCtorStatements.isEmpty())
             ${metadata.classNamePrefix}ClientConfiguration(const ${metadata.classNamePrefix}ClientConfiguration& other)
                 : Aws::Client::GenericClientConfiguration(other),
@@ -187,18 +175,6 @@ namespace ${rootNamespace}
             Aws::Crt::Optional<bool>& enableEndpointDiscovery;
 
 #end
-#if($serviceModel.endpointRuleSetModel.parameters.containsKey("AccountId"))
-            /**
-             * $serviceModel.endpointRuleSetModel.parameters["AccountId"].documentation
-             */
-            Aws::String accountId;
-#end
-#if($serviceModel.endpointRuleSetModel.parameters.containsKey("AccountIdEndpointMode"))
-            /**
-             * $serviceModel.endpointRuleSetModel.parameters["AccountIdEndpointMode"].documentation
-             */
-            Aws::String accountIdEndpointMode = "preferred";
-#end
 #if($serviceNamespace == "S3Crt")
 #parse("com/amazonaws/util/awsclientgenerator/velocity/cpp/s3/s3-crt/S3CrtClientConfigHeader.vm")
 #end
diff --git a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/common/ServiceClientConfigurationSource.vm b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/common/ServiceClientConfigurationSource.vm
index 123190b86e6..6f94e2e2202 100644
--- a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/common/ServiceClientConfigurationSource.vm
+++ b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/common/ServiceClientConfigurationSource.vm
@@ -123,19 +123,6 @@ void ${metadata.classNamePrefix}ClientConfiguration::Load${serviceNamespace}Spec
     enableEndpointDiscovery = IsEndpointDiscoveryEnabled(this->endpointOverride, inputProfileName);
   }
 #end
-#if($serviceModel.endpointRuleSetModel.parameters.containsKey("AccountId"))
-  // accountId is intentionally not set here: AWS_ACCOUNT_ID env variable may not match the provided credentials.
-  // it must be set by an auth provider / identity resolver or by an SDK user.
-#end
-#if($serviceModel.endpointRuleSetModel.parameters.containsKey("AccountIdEndpointMode"))
-  static const char AWS_ACCOUNT_ID_ENDPOINT_MODE_ENVIRONMENT_VARIABLE[] = "AWS_ACCOUNT_ID_ENDPOINT_MODE";
-  static const char AWS_ACCOUNT_ID_ENDPOINT_MODE_CONFIG_FILE_OPTION[] = "account_id_endpoint_mode";
-  accountIdEndpointMode = ClientConfiguration::LoadConfigFromEnvOrProfile(AWS_ACCOUNT_ID_ENDPOINT_MODE_ENVIRONMENT_VARIABLE,
-                                                                               inputProfileName,
-                                                                               AWS_ACCOUNT_ID_ENDPOINT_MODE_CONFIG_FILE_OPTION,
-                                                                               {"required", "disabled", "preferred"}, /* allowed values */
-                                                                               "preferred" /* default value */);
-#end
 }
 
 ${metadata.classNamePrefix}ClientConfiguration::${metadata.classNamePrefix}ClientConfiguration(const Client::ClientConfigurationInitValues &configuration)