diff --git a/codegen/aws-sdk-codegen/src/main/kotlin/aws/sdk/kotlin/codegen/endpoints/AwsBuiltins.kt b/codegen/aws-sdk-codegen/src/main/kotlin/aws/sdk/kotlin/codegen/endpoints/AwsBuiltins.kt
index c6e1924ea47..e149c10909a 100644
--- a/codegen/aws-sdk-codegen/src/main/kotlin/aws/sdk/kotlin/codegen/endpoints/AwsBuiltins.kt
+++ b/codegen/aws-sdk-codegen/src/main/kotlin/aws/sdk/kotlin/codegen/endpoints/AwsBuiltins.kt
@@ -6,6 +6,7 @@ package aws.sdk.kotlin.codegen.endpoints
 
 object AwsBuiltins {
     const val ACCOUNT_ID = "AWS::Auth::AccountId"
+    const val ACCOUNT_ID_ENDPOINT_MODE = "AWS::Auth::AccountIdEndpointMode"
     const val USE_FIPS = "AWS::UseFIPS"
     const val USE_DUAL_STACK = "AWS::UseDualStack"
     const val S3_ACCELERATE = "AWS::S3::Accelerate"
diff --git a/codegen/aws-sdk-codegen/src/main/kotlin/aws/sdk/kotlin/codegen/endpoints/BindAwsEndpointBuiltins.kt b/codegen/aws-sdk-codegen/src/main/kotlin/aws/sdk/kotlin/codegen/endpoints/BindAwsEndpointBuiltins.kt
index 5c418be243e..c4c49adc48f 100644
--- a/codegen/aws-sdk-codegen/src/main/kotlin/aws/sdk/kotlin/codegen/endpoints/BindAwsEndpointBuiltins.kt
+++ b/codegen/aws-sdk-codegen/src/main/kotlin/aws/sdk/kotlin/codegen/endpoints/BindAwsEndpointBuiltins.kt
@@ -106,6 +106,14 @@ fun renderBindAwsBuiltins(ctx: ProtocolGenerator.GenerationContext, writer: Kotl
                         AwsRuntimeTypes.Config.Endpoints.resolveAccountId,
                         AccountIdEndpointBuiltinCustomization.AccountIdEndpointModeProp.propertyName,
                     )
+
+                AwsBuiltins.ACCOUNT_ID_ENDPOINT_MODE -> {
+                    writer.write(
+                        "#L = config.#L.toString().lowercase()", // Spec specifies these enum values must be lowercase
+                        it.defaultName(),
+                        AccountIdEndpointBuiltinCustomization.AccountIdEndpointModeProp.propertyName,
+                    )
+                }
             }
         }
     }
diff --git a/codegen/aws-sdk-codegen/src/test/kotlin/aws/sdk/kotlin/codegen/endpoints/BindAwsEndpointBuiltinsTest.kt b/codegen/aws-sdk-codegen/src/test/kotlin/aws/sdk/kotlin/codegen/endpoints/BindAwsEndpointBuiltinsTest.kt
new file mode 100644
index 00000000000..2fa1877fe52
--- /dev/null
+++ b/codegen/aws-sdk-codegen/src/test/kotlin/aws/sdk/kotlin/codegen/endpoints/BindAwsEndpointBuiltinsTest.kt
@@ -0,0 +1,38 @@
+package aws.sdk.kotlin.codegen.endpoints
+
+import software.amazon.smithy.kotlin.codegen.core.KotlinWriter
+import software.amazon.smithy.kotlin.codegen.test.*
+import software.amazon.smithy.rulesengine.language.syntax.parameters.Parameter
+import software.amazon.smithy.rulesengine.language.syntax.parameters.ParameterType
+import kotlin.test.Test
+import kotlin.test.assertTrue
+
+class BindAwsEndpointBuiltinsTest {
+    @Test
+    fun testRenderAccountIdEndpointModeBuiltin() {
+        val model = "".prependNamespaceAndService().toSmithyModel()
+
+        val ctx = model.newTestContext().generationCtx
+        val writer = KotlinWriter(TestModelDefault.NAMESPACE)
+        val parameters = listOf(
+            Parameter
+                .builder()
+                .builtIn(AwsBuiltins.ACCOUNT_ID_ENDPOINT_MODE)
+                .type(ParameterType.STRING)
+                .name("accountIdEndpointMode")
+                .build(),
+        )
+
+        renderBindAwsBuiltins(
+            ctx,
+            writer,
+            parameters,
+        )
+
+        assertTrue(
+            writer
+                .rawString()
+                .contains("accountIdEndpointMode = config.accountIdEndpointMode.toString().lowercase()"),
+        )
+    }
+}
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index 6a4be30d30c..09b1b635bd2 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -12,8 +12,8 @@ atomicfu-version = "0.25.0"
 binary-compatibility-validator-version = "0.16.3"
 
 # smithy-kotlin codegen and runtime are versioned separately
-smithy-kotlin-runtime-version = "1.4.5"
-smithy-kotlin-codegen-version = "0.34.5"
+smithy-kotlin-runtime-version = "1.4.6"
+smithy-kotlin-codegen-version = "0.34.6"
 
 # codegen
 smithy-version = "1.53.0"