diff --git a/.changelog/account-id-endpoint-built-ins.md b/.changelog/account-id-endpoint-built-ins.md
new file mode 100644
index 0000000000000000000000000000000000000000..855b4755ea790087e6d383314cb3929f278ef95b
--- /dev/null
+++ b/.changelog/account-id-endpoint-built-ins.md
@@ -0,0 +1,10 @@
+---
+applies_to: ["aws-sdk-rust"]
+authors: ["landonxjames"]
+references: ["smithy-rs#3792"]
+breaking: false
+new_feature: false
+bug_fix: false
+---
+
+Add minimal support for `AWS::Auth::AccountId` and `AWS::Auth::AccountIdEndpointMode` endpoint built-ins
diff --git a/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/EndpointBuiltInsDecorator.kt b/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/EndpointBuiltInsDecorator.kt
index b2407859b516a630fc11128cf0c0b9349181782c..c23e2a6b86ca79e640aee45b4fd3c895d3ebb700 100644
--- a/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/EndpointBuiltInsDecorator.kt
+++ b/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/EndpointBuiltInsDecorator.kt
@@ -127,11 +127,14 @@ fun Model.sdkConfigSetter(
 
 /**
  * Create a client codegen decorator that creates bindings for a builtIn parameter. Optionally, you can provide
- * [clientParam.Builder] which allows control over the config parameter that will be generated.
+ * [clientParam.Builder] which allows control over the config parameter that will be generated. You can also opt
+ * to exclude including the extra sections that set the builtIn value on the SdkConfig. This is useful for builtIns
+ * that are only minimally supported, like accountId and accountIdEndpointMode.
  */
 fun decoratorForBuiltIn(
     builtIn: Parameter,
     clientParamBuilder: ConfigParam.Builder? = null,
+    includeSdkConfigSetter: Boolean = true,
 ): ClientCodegenDecorator {
     val nameOverride = clientParamBuilder?.name
     val name = nameOverride ?: builtIn.name.rustName()
@@ -143,9 +146,17 @@ fun decoratorForBuiltIn(
             codegenContext.getBuiltIn(builtIn) != null
 
         override fun extraSections(codegenContext: ClientCodegenContext): List<AdHocCustomization> {
-            return listOfNotNull(
-                codegenContext.model.sdkConfigSetter(codegenContext.serviceShape.id, builtIn, clientParamBuilder?.name),
-            )
+            if (includeSdkConfigSetter) {
+                return listOfNotNull(
+                    codegenContext.model.sdkConfigSetter(
+                        codegenContext.serviceShape.id,
+                        builtIn,
+                        clientParamBuilder?.name,
+                    ),
+                )
+            } else {
+                return listOf()
+            }
         }
 
         override fun configCustomizations(
@@ -236,4 +247,6 @@ val PromotedBuiltInsDecorators =
                 .type(RuntimeType.String.toSymbol())
                 .setterDocs(endpointUrlDocs),
         ),
+        decoratorForBuiltIn(AwsBuiltIns.ACCOUNT_ID_ENDPOINT_MODE, null, false),
+        decoratorForBuiltIn(AwsBuiltIns.ACCOUNT_ID, null, false),
     ).toTypedArray()
diff --git a/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/endpoints/OperationInputTestGenerator.kt b/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/endpoints/OperationInputTestGenerator.kt
index 5bcc870ae5bcf1d833e90d7b6de136ace1611543..489aef1d4efc0232c72a011268ce62ed600f6bb6 100644
--- a/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/endpoints/OperationInputTestGenerator.kt
+++ b/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/endpoints/OperationInputTestGenerator.kt
@@ -132,6 +132,7 @@ class OperationInputTestGenerator(_ctx: ClientCodegenContext, private val test:
             tokioTest(safeName("operation_input_test_$operationName")) {
                 rustTemplate(
                     """
+                    /* documentation: ${test.documentation.orElse("No docs :(")} */
                     /* builtIns: ${escape(Node.prettyPrintJson(testOperationInput.builtInParams))} */
                     /* clientParams: ${escape(Node.prettyPrintJson(testOperationInput.clientParams))} */
                     let (http_client, rcvr) = #{capture_request}(None);
@@ -211,6 +212,10 @@ class OperationInputTestGenerator(_ctx: ClientCodegenContext, private val test:
                         Logger.getLogger("OperationTestGenerator").warning("No provider for ${builtIn.value}")
                     }
                 }
+                // If the test contains Endpoint built-ins and does not contain an AWS::Region then we set one
+                if (!operationInput.builtInParams.isEmpty && !operationInput.builtInParams.containsMember("AWS::Region")) {
+                    rust("let builder = builder.region(::aws_types::region::Region::new(\"us-east-1\"));")
+                }
                 rust("builder.build()")
             }
         }
diff --git a/aws/sdk-codegen/src/test/kotlin/software/amazon/smithy/rustsdk/EndpointBuiltInsDecoratorTest.kt b/aws/sdk-codegen/src/test/kotlin/software/amazon/smithy/rustsdk/EndpointBuiltInsDecoratorTest.kt
index c5dd5581600f3e07c7a32f9406d703a2ebeb7d9b..61e83179194b4cb16560678560ad44925d417a58 100644
--- a/aws/sdk-codegen/src/test/kotlin/software/amazon/smithy/rustsdk/EndpointBuiltInsDecoratorTest.kt
+++ b/aws/sdk-codegen/src/test/kotlin/software/amazon/smithy/rustsdk/EndpointBuiltInsDecoratorTest.kt
@@ -21,23 +21,38 @@ class EndpointBuiltInsDecoratorTest {
         use aws.auth#sigv4
         use aws.protocols#restJson1
         use smithy.rules#endpointRuleSet
+        use smithy.rules#staticContextParams
 
         @service(sdkId: "dontcare")
         @restJson1
         @sigv4(name: "dontcare")
         @auth([sigv4])
+        @suppress(["RuleSetAwsBuiltIn.AWS::Auth::AccountId", "RuleSetAwsBuiltIn.AWS::Auth::AccountIdEndpointMode"])
         @endpointRuleSet({
             "version": "1.0"
             "parameters": {
                 "endpoint": { "required": false, "type": "string", "builtIn": "SDK::Endpoint" },
                 "region": { "required": false, "type": "String", "builtIn": "AWS::Region" },
+                "accountId": { "required": false, "type": "String", "builtIn": "AWS::Auth::AccountId" },
+                "accountIdEndpointMode": { "required": false, "type": "String", "builtIn": "AWS::Auth::AccountIdEndpointMode" },
             }
             "rules": [
                 {
                     "type": "endpoint"
                     "conditions": [
                         {"fn": "isSet", "argv": [{"ref": "endpoint"}]},
-                        {"fn": "isSet", "argv": [{"ref": "region"}]}
+                        {"fn": "isSet", "argv": [{"ref": "region"}]},
+                        {
+                            "fn": "not",
+                            "argv": [
+                                {
+                                    "fn": "isSet",
+                                    "argv": [
+                                        {"ref": "accountId"}
+                                    ]
+                                }
+                            ]
+                        }
                     ],
                     "endpoint": {
                         "url": "{endpoint}"
@@ -72,6 +87,11 @@ class EndpointBuiltInsDecoratorTest {
 
         @http(uri: "/SomeOperation", method: "GET")
         @optionalAuth
+        @staticContextParams(
+            accountIdEndpointMode: {
+                value: "some value"
+            }
+        )
         operation SomeOperation {
             output: SomeOutput
         }