diff --git a/aws-runtime/aws-config/build.gradle.kts b/aws-runtime/aws-config/build.gradle.kts
index f63ff328e44..e03be72f500 100644
--- a/aws-runtime/aws-config/build.gradle.kts
+++ b/aws-runtime/aws-config/build.gradle.kts
@@ -41,9 +41,6 @@ kotlin {
                 // additional dependencies required by generated sso provider(s)
                 implementation(libs.smithy.kotlin.aws.json.protocols)
 
-                // atomics
-                implementation(libs.kotlinx.atomicfu)
-
                 // coroutines
                 implementation(libs.kotlinx.coroutines.core)
             }
@@ -70,7 +67,7 @@ kotlin {
 }
 
 fun awsModelFile(name: String): String =
-    rootProject.file("codegen/sdk/aws-models/$name").relativeTo(project.buildDir).toString()
+    rootProject.file("codegen/sdk/aws-models/$name").relativeTo(project.layout.buildDirectory.get().asFile).toString()
 
 codegen {
     val basePackage = "aws.sdk.kotlin.runtime.auth.credentials.internal"
@@ -200,13 +197,17 @@ val codegenTask = tasks.named("generateSmithyProjections")
 tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompile> {
     dependsOn(codegenTask)
 
-    // generated sts/sso credential providers have quite a few warnings
-    kotlinOptions.allWarningsAsErrors = false
+    compilerOptions {
+        // generated sts/sso credential providers have quite a few warnings
+        allWarningsAsErrors.set(false)
+    }
 }
 
 tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinNativeCompile> {
     dependsOn(codegenTask)
-    kotlinOptions.allWarningsAsErrors = false
+    compilerOptions {
+        allWarningsAsErrors.set(false)
+    }
 }
 
 tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompileCommon> {
@@ -243,6 +244,7 @@ listOf("apiElements", "runtimeElements").forEach {
 
 // suppress internal generated clients
 tasks.named<DokkaTaskPartial>("dokkaHtmlPartial") {
+    dependsOn(codegenTask)
     dokkaSourceSets.configureEach {
         perPackageOption {
             matchingRegex.set(""".*\.internal.*""")
diff --git a/aws-runtime/build.gradle.kts b/aws-runtime/build.gradle.kts
index 3a1195ec12a..0365c85dee7 100644
--- a/aws-runtime/build.gradle.kts
+++ b/aws-runtime/build.gradle.kts
@@ -4,10 +4,10 @@
  */
 import aws.sdk.kotlin.gradle.dsl.configurePublishing
 import aws.sdk.kotlin.gradle.kmp.*
+import org.jetbrains.kotlin.gradle.dsl.JvmTarget
 
 description = "AWS client runtime support for generated service clients"
 
-@Suppress("DSL_SCOPE_VIOLATION") // TODO: Remove once https://youtrack.jetbrains.com/issue/KTIJ-19369 is fixed
 plugins {
     alias(libs.plugins.dokka)
     alias(libs.plugins.kotlinx.binary.compatibility.validator)
@@ -64,8 +64,14 @@ subprojects {
     }
 
     tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompile> {
-        kotlinOptions {
-            jvmTarget = "1.8"
+        compilerOptions {
+            jvmTarget.set(JvmTarget.JVM_1_8)
+            freeCompilerArgs.add("-Xexpect-actual-classes")
+        }
+    }
+    tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinNativeCompile> {
+        compilerOptions {
+            freeCompilerArgs.add("-Xexpect-actual-classes")
         }
     }
 }
diff --git a/build.gradle.kts b/build.gradle.kts
index 66d285405d8..b86cd23d06e 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -14,15 +14,18 @@ buildscript {
         classpath(libs.kotlinx.atomicfu.plugin)
         classpath("aws.sdk.kotlin:build-plugins") {
             version {
-                require("0.2.9")
+                require("0.3.0")
             }
         }
     }
 }
 
 plugins {
-    @Suppress("DSL_SCOPE_VIOLATION") // TODO: Remove once https://youtrack.jetbrains.com/issue/KTIJ-19369 is fixed
     alias(libs.plugins.dokka)
+    // ensure the correct version of KGP ends up on our buildscript classpath
+    // since build-plugins also has <some> version in its dependency closure
+    alias(libs.plugins.kotlin.multiplatform) apply false
+    alias(libs.plugins.kotlin.jvm) apply false
 }
 
 // configures (KMP) subprojects with our own KMP conventions and some default dependencies
diff --git a/codegen/aws-sdk-codegen/build.gradle.kts b/codegen/aws-sdk-codegen/build.gradle.kts
index 016d42acdcf..ce08be55758 100644
--- a/codegen/aws-sdk-codegen/build.gradle.kts
+++ b/codegen/aws-sdk-codegen/build.gradle.kts
@@ -1,9 +1,16 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+import org.jetbrains.kotlin.gradle.dsl.JvmTarget
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
 /*
  * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
  * SPDX-License-Identifier: Apache-2.0
  */
 plugins {
-    kotlin("jvm")
+    alias(libs.plugins.kotlin.jvm)
     jacoco
 }
 
@@ -38,7 +45,7 @@ dependencies {
 val generateSdkRuntimeVersion by tasks.registering {
     // generate the version of the runtime to use as a resource.
     // this keeps us from having to manually change version numbers in multiple places
-    val resourcesDir = "$buildDir/resources/main/aws/sdk/kotlin/codegen"
+    val resourcesDir = layout.buildDirectory.dir("resources/main/aws/sdk/kotlin/codegen").get()
     val versionFile = file("$resourcesDir/sdk-version.txt")
     val gradlePropertiesFile = rootProject.file("gradle.properties")
     inputs.file(gradlePropertiesFile)
@@ -49,20 +56,16 @@ val generateSdkRuntimeVersion by tasks.registering {
     }
 }
 
-val jvmTargetVersion = JavaVersion.VERSION_17.toString()
-
-tasks.compileKotlin {
-    kotlinOptions.jvmTarget = jvmTargetVersion
+tasks.withType<KotlinCompile> {
+    compilerOptions {
+        jvmTarget.set(JvmTarget.JVM_1_8)
+    }
     dependsOn(generateSdkRuntimeVersion)
 }
 
-tasks.compileTestKotlin {
-    kotlinOptions.jvmTarget = jvmTargetVersion
-}
-
 tasks.withType<JavaCompile> {
-    sourceCompatibility = jvmTargetVersion
-    targetCompatibility = jvmTargetVersion
+    sourceCompatibility = JavaVersion.VERSION_1_8.toString()
+    targetCompatibility = JavaVersion.VERSION_1_8.toString()
 }
 
 // Reusable license copySpec
@@ -94,9 +97,9 @@ tasks.test {
 // Configure jacoco (code coverage) to generate an HTML report
 tasks.jacocoTestReport {
     reports {
-        xml.isEnabled = false
-        csv.isEnabled = false
-        html.destination = file("$buildDir/reports/jacoco")
+        xml.required.set(false)
+        csv.required.set(false)
+        html.outputLocation.set(layout.buildDirectory.dir("reports/jacoco"))
     }
 }
 
diff --git a/codegen/aws-sdk-codegen/src/main/kotlin/aws/sdk/kotlin/codegen/GradleGenerator.kt b/codegen/aws-sdk-codegen/src/main/kotlin/aws/sdk/kotlin/codegen/GradleGenerator.kt
index 3a478c7d17f..0cae160ab7b 100644
--- a/codegen/aws-sdk-codegen/src/main/kotlin/aws/sdk/kotlin/codegen/GradleGenerator.kt
+++ b/codegen/aws-sdk-codegen/src/main/kotlin/aws/sdk/kotlin/codegen/GradleGenerator.kt
@@ -45,8 +45,6 @@ class GradleGenerator : KotlinIntegration {
         writer.write("project.ext.set(#S, #S)", "aws.sdk.id", ctx.settings.sdkId)
         writer.write("")
 
-        writer.write("val kotlinVersion: String by project")
-
         val allDependencies = delegator.dependencies.mapNotNull { it.properties["dependency"] as? KotlinDependency }.distinct()
 
         writer
diff --git a/codegen/smithy-aws-kotlin-codegen/build.gradle.kts b/codegen/smithy-aws-kotlin-codegen/build.gradle.kts
index a4b32102efa..f864936ae37 100644
--- a/codegen/smithy-aws-kotlin-codegen/build.gradle.kts
+++ b/codegen/smithy-aws-kotlin-codegen/build.gradle.kts
@@ -1,9 +1,16 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+import org.jetbrains.kotlin.gradle.dsl.JvmTarget
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
 /*
  * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
  * SPDX-License-Identifier: Apache-2.0
  */
 plugins {
-    kotlin("jvm")
+    alias(libs.plugins.kotlin.jvm)
     jacoco
 }
 
@@ -34,19 +41,15 @@ dependencies {
     testImplementation(libs.kotlinx.serialization.json)
 }
 
-val jvmTargetVersion = JavaVersion.VERSION_17.toString()
-
-tasks.compileKotlin {
-    kotlinOptions.jvmTarget = jvmTargetVersion
-}
-
-tasks.compileTestKotlin {
-    kotlinOptions.jvmTarget = jvmTargetVersion
+tasks.withType<KotlinCompile> {
+    compilerOptions {
+        jvmTarget.set(JvmTarget.JVM_1_8)
+    }
 }
 
 tasks.withType<JavaCompile> {
-    sourceCompatibility = jvmTargetVersion
-    targetCompatibility = jvmTargetVersion
+    sourceCompatibility = JavaVersion.VERSION_1_8.toString()
+    targetCompatibility = JavaVersion.VERSION_1_8.toString()
 }
 
 // Reusable license copySpec
@@ -78,9 +81,9 @@ tasks.test {
 // Configure jacoco (code coverage) to generate an HTML report
 tasks.jacocoTestReport {
     reports {
-        xml.isEnabled = false
-        csv.isEnabled = false
-        html.destination = file("$buildDir/reports/jacoco")
+        xml.required.set(false)
+        csv.required.set(false)
+        html.outputLocation.set(layout.buildDirectory.dir("reports/jacoco"))
     }
 }
 
diff --git a/dokka-aws/build.gradle.kts b/dokka-aws/build.gradle.kts
index f469a769443..e93f6aeb756 100644
--- a/dokka-aws/build.gradle.kts
+++ b/dokka-aws/build.gradle.kts
@@ -1,9 +1,16 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+import org.jetbrains.kotlin.gradle.dsl.JvmTarget
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
 /*
  * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
  * SPDX-License-Identifier: Apache-2.0
  */
 plugins {
-    kotlin("jvm")
+    alias(libs.plugins.kotlin.jvm)
 }
 
 description = "Custom Dokka plugin for AWS Kotlin SDK API docs"
@@ -13,9 +20,14 @@ dependencies {
     compileOnly(libs.dokka.core)
 }
 
-tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompile> {
-    kotlinOptions {
-        jvmTarget = "1.8"
-        allWarningsAsErrors = false // FIXME Dokka bundles stdlib into the classpath, causing an unfixable warning
+tasks.withType<KotlinCompile> {
+    compilerOptions {
+        jvmTarget.set(JvmTarget.JVM_1_8)
+        allWarningsAsErrors.set(false) // FIXME Dokka bundles stdlib into the classpath, causing an unfixable warning
     }
 }
+
+tasks.withType<JavaCompile> {
+    sourceCompatibility = JavaVersion.VERSION_1_8.toString()
+    targetCompatibility = JavaVersion.VERSION_1_8.toString()
+}
diff --git a/gradle.properties b/gradle.properties
index ee25ba8ffe6..645bc23f6bd 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -8,11 +8,10 @@ org.gradle.jvmargs=-Xmx6g -XX:MaxMetaspaceSize=2G
 # sdk
 sdkVersion=1.0.18-SNAPSHOT
 
-# kotlin
-kotlinVersion=1.9.20
-
 # dokka config (values specified at build-time as needed)
 smithyKotlinDocBaseUrl=https://sdk.amazonaws.com/kotlin/api/smithy-kotlin/api/$smithyKotlinRuntimeVersion/
 
 # atomicfu
-kotlinx.atomicfu.enableJvmIrTransformation=true
\ No newline at end of file
+kotlinx.atomicfu.enableJvmIrTransformation=true
+# FIXME - https://github.com/Kotlin/kotlinx-atomicfu/issues/274
+kotlinx.atomicfu.enableNativeIrTransformation=false
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index 62be89ec553..a930e952a15 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -1,10 +1,10 @@
 [versions]
-kotlin-version = "1.9.20"
+kotlin-version = "1.9.21"
 dokka-version = "1.9.10"
 
 # libs
 coroutines-version = "1.7.3"
-atomicfu-version = "0.22.0"
+atomicfu-version = "0.23.1"
 
 # smithy-kotlin codegen and runtime are versioned separately
 smithy-kotlin-runtime-version = "1.0.4"
diff --git a/gradle/wrapper/gradle-wrapper.jar b/gradle/wrapper/gradle-wrapper.jar
index 7454180f2ae..afba109285a 100644
Binary files a/gradle/wrapper/gradle-wrapper.jar and b/gradle/wrapper/gradle-wrapper.jar differ
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index 068cdb2dc26..3499ded5c11 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,5 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-7.6.3-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.5-bin.zip
+networkTimeout=10000
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
diff --git a/gradlew b/gradlew
index 1b6c787337f..65dcd68d65c 100755
--- a/gradlew
+++ b/gradlew
@@ -55,7 +55,7 @@
 #       Darwin, MinGW, and NonStop.
 #
 #   (3) This script is generated from the Groovy template
-#       https://github.com/gradle/gradle/blob/master/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       https://github.com/gradle/gradle/blob/HEAD/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
 #       within the Gradle project.
 #
 #       You can find Gradle at https://github.com/gradle/gradle/.
@@ -80,10 +80,10 @@ do
     esac
 done
 
-APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
-
-APP_NAME="Gradle"
+# This is normally unused
+# shellcheck disable=SC2034
 APP_BASE_NAME=${0##*/}
+APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
 
 # Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
 DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
@@ -143,12 +143,16 @@ fi
 if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
     case $MAX_FD in #(
       max*)
+        # In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC3045 
         MAX_FD=$( ulimit -H -n ) ||
             warn "Could not query maximum file descriptor limit"
     esac
     case $MAX_FD in  #(
       '' | soft) :;; #(
       *)
+        # In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC3045 
         ulimit -n "$MAX_FD" ||
             warn "Could not set maximum file descriptor limit to $MAX_FD"
     esac
@@ -205,6 +209,12 @@ set -- \
         org.gradle.wrapper.GradleWrapperMain \
         "$@"
 
+# Stop when "xargs" is not available.
+if ! command -v xargs >/dev/null 2>&1
+then
+    die "xargs is not available"
+fi
+
 # Use "xargs" to parse quoted args.
 #
 # With -n1 it outputs one arg per line, with the quotes and backslashes removed.
diff --git a/gradlew.bat b/gradlew.bat
index ac1b06f9382..6689b85beec 100644
--- a/gradlew.bat
+++ b/gradlew.bat
@@ -14,7 +14,7 @@
 @rem limitations under the License.
 @rem
 
-@if "%DEBUG%" == "" @echo off
+@if "%DEBUG%"=="" @echo off
 @rem ##########################################################################
 @rem
 @rem  Gradle startup script for Windows
@@ -25,7 +25,8 @@
 if "%OS%"=="Windows_NT" setlocal
 
 set DIRNAME=%~dp0
-if "%DIRNAME%" == "" set DIRNAME=.
+if "%DIRNAME%"=="" set DIRNAME=.
+@rem This is normally unused
 set APP_BASE_NAME=%~n0
 set APP_HOME=%DIRNAME%
 
@@ -40,7 +41,7 @@ if defined JAVA_HOME goto findJavaFromJavaHome
 
 set JAVA_EXE=java.exe
 %JAVA_EXE% -version >NUL 2>&1
-if "%ERRORLEVEL%" == "0" goto execute
+if %ERRORLEVEL% equ 0 goto execute
 
 echo.
 echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
@@ -75,13 +76,15 @@ set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
 
 :end
 @rem End local scope for the variables with windows NT shell
-if "%ERRORLEVEL%"=="0" goto mainEnd
+if %ERRORLEVEL% equ 0 goto mainEnd
 
 :fail
 rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
 rem the _cmd.exe /c_ return code!
-if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
-exit /b 1
+set EXIT_CODE=%ERRORLEVEL%
+if %EXIT_CODE% equ 0 set EXIT_CODE=1
+if not ""=="%GRADLE_EXIT_CONSOLE%" exit %EXIT_CODE%
+exit /b %EXIT_CODE%
 
 :mainEnd
 if "%OS%"=="Windows_NT" endlocal
diff --git a/services/build.gradle.kts b/services/build.gradle.kts
index c69d367bac7..e5912af66ea 100644
--- a/services/build.gradle.kts
+++ b/services/build.gradle.kts
@@ -5,11 +5,11 @@
 import aws.sdk.kotlin.gradle.dsl.configurePublishing
 import aws.sdk.kotlin.gradle.kmp.*
 import aws.sdk.kotlin.gradle.util.typedProp
+import org.jetbrains.kotlin.gradle.dsl.JvmTarget
 import java.time.LocalDateTime
 
 plugins {
     `maven-publish`
-    @Suppress("DSL_SCOPE_VIOLATION") // TODO: Remove once https://youtrack.jetbrains.com/issue/KTIJ-19369 is fixed
     alias(libs.plugins.dokka)
 }
 
@@ -117,9 +117,9 @@ subprojects {
     }
 
     tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompile> {
-        kotlinOptions {
-            allWarningsAsErrors = false // FIXME Tons of errors occur in generated code
-            jvmTarget = "1.8" // fixes outgoing variant metadata: https://github.com/awslabs/smithy-kotlin/issues/258
+        compilerOptions {
+            allWarningsAsErrors.set(false) // FIXME Tons of errors occur in generated code
+            jvmTarget.set(JvmTarget.JVM_1_8) // fixes outgoing variant metadata: https://github.com/awslabs/smithy-kotlin/issues/258
         }
     }
 
diff --git a/settings.gradle.kts b/settings.gradle.kts
index 56e0ff1fd14..84aa67eb10b 100644
--- a/settings.gradle.kts
+++ b/settings.gradle.kts
@@ -9,13 +9,6 @@ pluginManagement {
         mavenCentral()
         gradlePluginPortal()
     }
-
-    // configure default plugin versions
-    plugins {
-        val kotlinVersion: String by settings
-        id("org.jetbrains.kotlin.jvm") version kotlinVersion
-        id("org.jetbrains.kotlin.multiplatform") version kotlinVersion
-    }
 }
 
 dependencyResolutionManagement {
diff --git a/tests/benchmarks/service-benchmarks/build.gradle.kts b/tests/benchmarks/service-benchmarks/build.gradle.kts
index 98d956d2541..0366b195e90 100644
--- a/tests/benchmarks/service-benchmarks/build.gradle.kts
+++ b/tests/benchmarks/service-benchmarks/build.gradle.kts
@@ -5,7 +5,7 @@
 import aws.sdk.kotlin.gradle.dsl.skipPublishing
 
 plugins {
-    kotlin("multiplatform")
+    alias(libs.plugins.kotlin.multiplatform)
     application
 }
 
diff --git a/tests/codegen/event-stream/build.gradle.kts b/tests/codegen/event-stream/build.gradle.kts
index 82ac7b29a8e..e7c5c1bcfb5 100644
--- a/tests/codegen/event-stream/build.gradle.kts
+++ b/tests/codegen/event-stream/build.gradle.kts
@@ -6,7 +6,7 @@ import aws.sdk.kotlin.gradle.codegen.dsl.smithyKotlinPlugin
 import software.amazon.smithy.gradle.tasks.SmithyBuild
 
 plugins {
-    kotlin("jvm")
+    alias(libs.plugins.kotlin.jvm)
     id("aws.sdk.kotlin.codegen")
 }
 
@@ -22,7 +22,7 @@ data class EventStreamTest(
     val modelTemplate: File,
 ) {
     val model: File
-        get() = buildDir.resolve("$projectionName/model.smithy")
+        get() = layout.buildDirectory.file("$projectionName/model.smithy").get().asFile
 }
 
 val tests = listOf(
diff --git a/tests/e2e-test-util/build.gradle.kts b/tests/e2e-test-util/build.gradle.kts
index d8f8d2cd7f3..4e476ce6af6 100644
--- a/tests/e2e-test-util/build.gradle.kts
+++ b/tests/e2e-test-util/build.gradle.kts
@@ -3,7 +3,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 plugins {
-    kotlin("jvm")
+    alias(libs.plugins.kotlin.jvm)
 }
 
 description = "Test utilities for integration and e2e tests"