diff --git a/CHANGELOG.md b/CHANGELOG.md
index 610bfc32b..898a87d5b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+# 0.18.10
+
+* Bumps alloy to 0.3.1. This is required as otherwise the `alloy#nullable` hints get filtered out when using SimpleRestJsonBuilder.
+
 # 0.18.9
 
 * Fix bug that would lead to special characters being escaped in XML attributes, which are already quoted
diff --git a/build.sbt b/build.sbt
index 5239f82f7..2445b8da7 100644
--- a/build.sbt
+++ b/build.sbt
@@ -314,7 +314,7 @@ lazy val `aws-http4s` = projectMatrix
       "-Wconf:msg=value noErrorWrapping in class RestXml is deprecated:silent"
     ),
     Test / complianceTestDependencies := Seq(
-      Dependencies.Alloy.`protocol-tests`
+      Dependencies.Smithy.`aws-protocol-tests`
     ),
     (Test / resourceGenerators) := Seq(dumpModel(Test).taskValue),
     (Test / smithy4sModelTransformers) := Seq.empty,
diff --git a/modules/aws-http4s/test/src/smithy4s/aws/compliancetests/AwsComplianceSuite.scala b/modules/aws-http4s/test/src/smithy4s/aws/compliancetests/AwsComplianceSuite.scala
index 0cea7b8e6..8f32f44a7 100644
--- a/modules/aws-http4s/test/src/smithy4s/aws/compliancetests/AwsComplianceSuite.scala
+++ b/modules/aws-http4s/test/src/smithy4s/aws/compliancetests/AwsComplianceSuite.scala
@@ -47,7 +47,19 @@ object AwsComplianceSuite extends ProtocolComplianceSuite {
       "HostWithPathOperation",
       // We expect users to set idempotency tokens because doing so raises
       // awareness of the need to do so outside of any retry mechanism.
-      "QueryIdempotencyTokenAutoFill"
+      "QueryIdempotencyTokenAutoFill",
+
+      // TODO https://github.com/disneystreaming/smithy4s/issues/1424
+      "AwsJson10DeserializeIgnoreType",
+      "AwsJson10ClientPopulatesDefaultValuesInInput",
+      "AwsJson10ClientPopulatesDefaultsValuesWhenMissingInResponse",
+      "AwsJson10ClientPopulatesNestedDefaultValuesWhenMissing",
+      "AwsJson10ClientPopulatesNestedDefaultsWhenMissingInResponseBody",
+      "AwsJson10ClientErrorCorrectsWhenServerFailsToSerializeRequiredValues",
+      "AwsJson11DeserializeIgnoreType",
+      "RestJsonHttpPayloadWithUnsetUnion",
+      "RestJsonDeserializeIgnoreType",
+      "RestXmlHttpPayloadWithUnsetUnion"
     )
     (complianceTest: ComplianceTest[IO]) =>
       if (disallowed.exists(complianceTest.show.contains(_))) ShouldRun.No
diff --git a/modules/codegen-plugin/src/sbt-test/codegen-plugin/defaults/build.sbt b/modules/codegen-plugin/src/sbt-test/codegen-plugin/defaults/build.sbt
index 3e607fca3..15ce75672 100644
--- a/modules/codegen-plugin/src/sbt-test/codegen-plugin/defaults/build.sbt
+++ b/modules/codegen-plugin/src/sbt-test/codegen-plugin/defaults/build.sbt
@@ -10,7 +10,7 @@ lazy val root = (project in file("."))
       val expectedLines = Set(
         "version",
         "src/main/smithy",
-        "com.disneystreaming.alloy:alloy-core:0.2.8"
+        s"com.disneystreaming.alloy:alloy-core:${smithy4s.codegen.BuildInfo.alloyVersion}"
       )
       val content =
         IO.readLines(baseDirectory.value / "smithy-build.json")
diff --git a/modules/codegen-plugin/src/sbt-test/codegen-plugin/multimodule/build.sbt b/modules/codegen-plugin/src/sbt-test/codegen-plugin/multimodule/build.sbt
index c2c173aff..9a4f1f959 100644
--- a/modules/codegen-plugin/src/sbt-test/codegen-plugin/multimodule/build.sbt
+++ b/modules/codegen-plugin/src/sbt-test/codegen-plugin/multimodule/build.sbt
@@ -8,7 +8,7 @@ lazy val root = project
         "version",
         "src/main/smithy",
         "software.amazon.smithy:smithy-waiters:1.38.0",
-        "com.disneystreaming.alloy:alloy-core:0.2.8",
+        s"com.disneystreaming.alloy:alloy-core:${smithy4s.codegen.BuildInfo.alloyVersion}",
         "com.disneystreaming.smithy4s:smithy4s-protocol:",
         "custom",
         "attribute"
diff --git a/modules/codegen/src/smithy4s/codegen/internals/CodegenImpl.scala b/modules/codegen/src/smithy4s/codegen/internals/CodegenImpl.scala
index bda3526c2..da84ce768 100644
--- a/modules/codegen/src/smithy4s/codegen/internals/CodegenImpl.scala
+++ b/modules/codegen/src/smithy4s/codegen/internals/CodegenImpl.scala
@@ -26,6 +26,7 @@ import software.amazon.smithy.model.node.Node
 import software.amazon.smithy.model.shapes.ModelSerializer
 
 import scala.jdk.CollectionConverters._
+import software.amazon.smithy.model.transform.ModelTransformer
 
 private[codegen] object CodegenImpl { self =>
 
@@ -179,8 +180,12 @@ private[codegen] object CodegenImpl { self =>
       discoverModels = false,
       args.localJars
     )
+    val flattenedModel =
+      ModelTransformer.create().flattenAndRemoveMixins(model)
 
-    Node.prettyPrintJson(ModelSerializer.builder().build.serialize(model))
+    Node.prettyPrintJson(
+      ModelSerializer.builder().build.serialize(flattenedModel)
+    )
   }
 
   private def withAwsTypeTransformer(transformers: List[String]): List[String] =
diff --git a/project/Dependencies.scala b/project/Dependencies.scala
index 7ab81642f..9064e6452 100644
--- a/project/Dependencies.scala
+++ b/project/Dependencies.scala
@@ -25,11 +25,12 @@ object Dependencies {
     val build = org % "smithy-build" % smithyVersion
     val awsTraits = org % "smithy-aws-traits" % smithyVersion
     val waiters = org % "smithy-waiters" % smithyVersion
+    val `aws-protocol-tests` = org % "smithy-aws-protocol-tests" % smithyVersion
   }
 
   val Alloy = new {
     val org = "com.disneystreaming.alloy"
-    val alloyVersion = "0.2.8"
+    val alloyVersion = "0.3.1"
     val core = org % "alloy-core" % alloyVersion
     val openapi = org %% "alloy-openapi" % alloyVersion
     val `protocol-tests` = org % "alloy-protocol-tests" % alloyVersion