diff --git a/.github/actions/setup-build/action.yml b/.github/actions/setup-build/action.yml
new file mode 100644
index 000000000..0a2b5cbb9
--- /dev/null
+++ b/.github/actions/setup-build/action.yml
@@ -0,0 +1,39 @@
+name: Setup Build
+description: >
+  Checkout repositories and build dependencies
+
+runs:
+  using: composite
+  steps:
+    - name: Checkout tools
+      uses: actions/checkout@v4
+      with:
+        path: 'aws-kotlin-repo-tools'
+        repository: 'awslabs/aws-kotlin-repo-tools'
+        sparse-checkout: |
+          .github
+
+    - name: Checkout aws-crt-kotlin
+      uses: ./aws-kotlin-repo-tools/.github/actions/checkout-head
+      with:
+        # checkout aws-crt-kotlin as a sibling which will automatically make it an included build
+        path: 'aws-crt-kotlin'
+        repository: 'awslabs/aws-crt-kotlin'
+
+    # Cache the Kotlin/Native toolchain based on the input Kotlin version from version catalog
+    # see https://kotlinlang.org/docs/native-improving-compilation-time.html
+    - name: Cache Kotlin Native toolchain
+      uses: actions/cache@v4
+      with:
+        path: |
+          ~/.konan
+        key: ${{ runner.os }}-konan-${{ hashFiles('gradle/libs.versions.toml') }}
+        restore-keys: |
+          ${{ runner.os }}-konan-
+
+    - name: Configure JDK
+      uses: actions/setup-java@v3
+      with:
+        distribution: 'corretto'
+        java-version: 17
+        cache: 'gradle'
\ No newline at end of file
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 000000000..45b7b9cac
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,192 @@
+name: CI
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+  workflow_dispatch:
+
+# Allow one instance of this workflow per pull request, and cancel older runs when new changes are pushed
+concurrency:
+  group: ci-pr-${{ github.ref }}
+  cancel-in-progress: true
+
+env:
+  RUN: ${{ github.run_id }}-${{ github.run_number }}
+  GRADLE_OPTS: "-Dorg.gradle.daemon=false -Dkotlin.incremental=false"
+
+jobs:
+  jvm:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        # we build with a specific JDK version but source/target compatibility should ensure the jar is usable by
+        # the target versions we want to support
+        java-version:
+          - 8
+          - 11
+          - 17
+          - 21
+    steps:
+      - name: Checkout sources
+        uses: actions/checkout@v4
+        with:
+          path: 'smithy-kotlin'
+
+      - name: Setup build
+        uses: ./smithy-kotlin/.github/actions/setup-build
+
+      - name: Build and Test on JVM
+        working-directory: ./smithy-kotlin
+        shell: bash
+        run: |
+          ./gradlew -Paws.kotlin.native=false -Ptest.java.version=${{ matrix.java-version }} jvmTest --stacktrace
+
+  # macos-14 build and test for targets: jvm, macoArm64, iosSimulatorArm64, watchosSimulatorArm65, tvosSimulatorArm64
+  # macos-13 build and test for targets: jvm, macoX64, iosX64, tvosX64, watchosX64
+  macos:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [macos-14, macos-13]
+    runs-on: ${{ matrix.os }}
+    steps:
+      - name: Checkout sources
+        uses: actions/checkout@v4
+        with:
+          path: 'smithy-kotlin'
+
+      - name: Setup build
+        uses: ./smithy-kotlin/.github/actions/setup-build
+
+      - name: Build and Test on Apple platforms
+        working-directory: ./smithy-kotlin
+        shell: bash
+        run: |
+          # FIXME K2. Re-enable warnings as errors after this warning is removed: https://youtrack.jetbrains.com/issue/KT-68532
+          # echo "kotlinWarningsAsErrors=true" >> $GITHUB_WORKSPACE/local.properties              
+          ./gradlew apiCheck
+          ./gradlew -Paws.sdk.kotlin.crt.disableCrossCompile=true build
+
+      - name: Save Test Reports
+        if: failure()
+        uses: actions/upload-artifact@v3
+        with:
+          name: test-reports-${{ matrix.os }}
+          path: '**/build/reports'
+
+  # build and test for targets: jvm, linuxX64
+  # cross compile for: linuxX64, linuxArm64
+  # TODO - add mingw as cross compile target
+  linux:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout sources
+        uses: actions/checkout@v4
+        with:
+          path: 'smithy-kotlin'
+
+      - name: Setup build
+        uses: ./smithy-kotlin/.github/actions/setup-build
+
+      - name: Configure CRT Docker Images
+        run: |
+          ./aws-crt-kotlin/docker-images/build-all.sh
+
+      - name: Build and Test on Linux with Cross-Compile
+        working-directory: ./smithy-kotlin
+        shell: bash
+        run: |
+          # FIXME K2. Re-enable warnings as errors after this warning is removed: https://youtrack.jetbrains.com/issue/KT-68532
+          # echo "kotlinWarningsAsErrors=true" >> $GITHUB_WORKSPACE/local.properties
+          ./gradlew apiCheck
+          ./gradlew build
+
+      - name: Save Test Reports
+        if: failure()
+        uses: actions/upload-artifact@v3
+        with:
+          name: test-reports-${{ matrix.os }}
+          path: '**/build/reports'
+
+  # windows JVM
+  windows:
+    runs-on: windows-2022
+    steps:
+      - name: Checkout sources
+        uses: actions/checkout@v4
+        with:
+          path: 'smithy-kotlin'
+
+      - name: Setup build
+        uses: ./smithy-kotlin/.github/actions/setup-build
+
+      - name: Build and Test on Windows JVM
+        working-directory: ./smithy-kotlin
+        run: |
+          ./gradlew apiCheck
+          ./gradlew -P"aws.sdk.kotlin.crt.disableCrossCompile"=true build
+
+      - name: Save Test Reports
+        if: failure()
+        uses: actions/upload-artifact@v4
+        with:
+          name: test-reports-windows
+          path: '**/build/reports'
+
+  protocol-tests:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout sources
+        uses: actions/checkout@v4
+        with:
+          path: 'smithy-kotlin'
+
+      - name: Setup build
+        uses: ./smithy-kotlin/.github/actions/setup-build
+
+      - name: Test
+        working-directory: ./smithy-kotlin
+        shell: bash
+        run: |
+          ./gradlew -Paws.kotlin.native=false publishToMavenLocal
+          ./gradlew -Paws.kotlin.native=false testAllProtocols
+
+  downstream:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout sources
+      uses: actions/checkout@v4
+      with:
+        path: 'smithy-kotlin'
+
+    - name: Setup build
+      uses: ./smithy-kotlin/.github/actions/setup-build
+
+    - name: Checkout aws-sdk-kotlin
+      uses: ./aws-kotlin-repo-tools/.github/actions/checkout-head
+      with:
+        # smithy-kotlin is checked out as a sibling dir which will automatically make it an included build
+        path: 'aws-sdk-kotlin'
+        repository: 'awslabs/aws-sdk-kotlin'
+
+    - name: Build and Test aws-sdk-kotlin downstream
+      working-directory: ./smithy-kotlin
+      run: |
+        # TODO - JVM only
+        cd $GITHUB_WORKSPACE/smithy-kotlin
+        ./gradlew --parallel -Paws.kotlin.native=false publishToMavenLocal
+        SMITHY_KOTLIN_RUNTIME_VERSION=$(grep sdkVersion= gradle.properties | cut -d = -f 2)
+        SMITHY_KOTLIN_CODEGEN_VERSION=$(grep codegenVersion= gradle.properties | cut -d = -f 2)
+        cd $GITHUB_WORKSPACE/aws-sdk-kotlin
+        # replace smithy-kotlin-runtime-version and smithy-kotlin-codegen-version to be
+        # whatever we are testing such that the protocol test projects don't fail with a
+        # version that doesn't exist locally or in maven central. Otherwise the generated
+        # protocol test projects will use whatever the SDK thinks the version of
+        # smithy-kotlin should be
+        sed -i "s/smithy-kotlin-runtime-version = .*$/smithy-kotlin-runtime-version = \"$SMITHY_KOTLIN_RUNTIME_VERSION\"/" gradle/libs.versions.toml
+        sed -i "s/smithy-kotlin-codegen-version = .*$/smithy-kotlin-codegen-version = \"$SMITHY_KOTLIN_CODEGEN_VERSION\"/" gradle/libs.versions.toml
+        ./gradlew --parallel -Paws.kotlin.native=false publishToMavenLocal
+        ./gradlew -Paws.kotlin.native=false test jvmTest
+        ./gradlew -Paws.kotlin.native=false testAllProtocols
\ No newline at end of file
diff --git a/.github/workflows/continuous-integration.yml b/.github/workflows/continuous-integration.yml
deleted file mode 100644
index 9b0dc1c88..000000000
--- a/.github/workflows/continuous-integration.yml
+++ /dev/null
@@ -1,135 +0,0 @@
-name: CI
-
-on:
-  push:
-    branches: [ main ]
-  pull_request:
-  workflow_dispatch:
-
-# Allow one instance of this workflow per pull request, and cancel older runs when new changes are pushed
-concurrency:
-  group: ci-pr-${{ github.ref }}
-  cancel-in-progress: true
-
-env:
-  RUN: ${{ github.run_id }}-${{ github.run_number }}
-  GRADLE_OPTS: "-Dorg.gradle.daemon=false -Dkotlin.incremental=false"
-
-jobs:
-  jvm:
-    runs-on: ubuntu-latest
-    strategy:
-      fail-fast: false
-      matrix:
-        # we build with a specific JDK version but source/target compatibility should ensure the jar is usable by
-        # the target versions we want to support
-        java-version:
-          - 8
-          - 11
-          - 17
-          - 21
-    steps:
-      - name: Checkout sources
-        uses: actions/checkout@v4
-      - name: Configure JDK
-        uses: actions/setup-java@v3
-        with:
-          distribution: 'corretto'
-          java-version: 17
-          cache: 'gradle'
-      - name: Test
-        shell: bash
-        run: |
-          ./gradlew -Ptest.java.version=${{ matrix.java-version }} jvmTest --stacktrace
-
-  all-platforms:
-    runs-on: ${{ matrix.os }}
-    strategy:
-      fail-fast: false
-      matrix:
-        os: [ ubuntu-latest, macos-latest, windows-latest ]
-    steps:
-      - name: Checkout sources
-        uses: actions/checkout@v4
-      - name: Configure JDK
-        uses: actions/setup-java@v3
-        with:
-          distribution: 'corretto'
-          java-version: 17
-          cache: 'gradle'
-      - name: Test
-        shell: bash
-        run: |
-          # FIXME K2. Re-enable warnings as errors after this warning is removed: https://youtrack.jetbrains.com/issue/KT-68532
-          # echo "kotlinWarningsAsErrors=true" >> $GITHUB_WORKSPACE/local.properties              
-          ./gradlew apiCheck
-          ./gradlew test jvmTest
-      - name: Save Test Reports
-        if: failure()
-        uses: actions/upload-artifact@v3
-        with:
-          name: test-reports-${{ matrix.os }}
-          path: '**/build/reports'
-
-  protocol-tests:
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout sources
-        uses: actions/checkout@v4
-      - name: Configure JDK
-        uses: actions/setup-java@v3
-        with:
-          distribution: 'corretto'
-          java-version: 17
-          cache: 'gradle'
-      - name: Test
-        shell: bash
-        run: |
-          ./gradlew publishToMavenLocal
-          ./gradlew testAllProtocols
-
-  downstream:
-    runs-on: ubuntu-latest
-    steps:
-    - name: Checkout sources
-      uses: actions/checkout@v4
-      with:
-        path: 'smithy-kotlin'
-    - name: Checkout tools
-      uses: actions/checkout@v4
-      with:
-        path: 'aws-kotlin-repo-tools'
-        repository: 'awslabs/aws-kotlin-repo-tools'
-        ref: '0.2.3'
-        sparse-checkout: |
-          .github
-    - name: Checkout aws-sdk-kotlin
-      uses: ./aws-kotlin-repo-tools/.github/actions/checkout-head
-      with:
-        # smithy-kotlin is checked out as a sibling dir which will automatically make it an included build
-        path: 'aws-sdk-kotlin'
-        repository: 'awslabs/aws-sdk-kotlin'
-    - name: Configure JDK
-      uses: actions/setup-java@v3
-      with:
-        distribution: 'corretto'
-        java-version: 17
-        cache: 'gradle'
-    - name: Build and Test aws-sdk-kotlin downstream
-      run: |
-        # TODO - JVM only
-        cd $GITHUB_WORKSPACE/smithy-kotlin
-        ./gradlew --parallel publishToMavenLocal
-        SMITHY_KOTLIN_RUNTIME_VERSION=$(grep sdkVersion= gradle.properties | cut -d = -f 2)
-        SMITHY_KOTLIN_CODEGEN_VERSION=$(grep codegenVersion= gradle.properties | cut -d = -f 2)
-        cd $GITHUB_WORKSPACE/aws-sdk-kotlin
-        # replace smithy-kotlin-runtime-version and smithy-kotlin-codegen-version to be
-        # whatever we are testing such that the protocol test projects don't fail with a
-        # version that doesn't exist locally or in maven central. Otherwise the generated
-        # protocol test projects will use whatever the SDK thinks the version of
-        # smithy-kotlin should be
-        sed -i "s/smithy-kotlin-runtime-version = .*$/smithy-kotlin-runtime-version = \"$SMITHY_KOTLIN_RUNTIME_VERSION\"/" gradle/libs.versions.toml
-        sed -i "s/smithy-kotlin-codegen-version = .*$/smithy-kotlin-codegen-version = \"$SMITHY_KOTLIN_CODEGEN_VERSION\"/" gradle/libs.versions.toml
-        ./gradlew --parallel publishToMavenLocal
-        ./gradlew test jvmTest
-        ./gradlew testAllProtocols
\ No newline at end of file
diff --git a/.gitignore b/.gitignore
index 225fe6070..a776ae3ff 100644
--- a/.gitignore
+++ b/.gitignore
@@ -47,3 +47,5 @@ gradle-app.setting
 
 # MacOS
 .DS_Store
+
+*.cinteropLibraries.json
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index eb5170e4c..f52b1a56c 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -2,7 +2,7 @@
 kotlin-version = "2.0.21"
 dokka-version = "1.9.10"
 
-aws-kotlin-repo-tools-version = "0.4.13"
+aws-kotlin-repo-tools-version = "0.4.15-kn"
 
 # libs
 coroutines-version = "1.9.0"
@@ -91,6 +91,7 @@ docker-transport-zerodep = { module = "com.github.docker-java:docker-java-transp
 ktor-http-cio = { module = "io.ktor:ktor-http-cio", version.ref = "ktor-version" }
 ktor-utils = { module = "io.ktor:ktor-utils", version.ref = "ktor-version" }
 ktor-io = { module = "io.ktor:ktor-io", version.ref = "ktor-version" }
+ktor-server-core = { module = "io.ktor:ktor-server-core", version.ref = "ktor-version" }
 ktor-server-netty = { module = "io.ktor:ktor-server-netty", version.ref = "ktor-version" }
 ktor-server-jetty-jakarta = { module = "io.ktor:ktor-server-jetty-jakarta", version.ref = "ktor-version" }
 ktor-server-cio = { module = "io.ktor:ktor-server-cio", version.ref = "ktor-version" }
diff --git a/runtime/auth/aws-signing-crt/build.gradle.kts b/runtime/auth/aws-signing-crt/build.gradle.kts
index 4c6728276..5dddb3f45 100644
--- a/runtime/auth/aws-signing-crt/build.gradle.kts
+++ b/runtime/auth/aws-signing-crt/build.gradle.kts
@@ -8,14 +8,14 @@ extra["moduleName"] = "aws.smithy.kotlin.runtime.auth.awssigning.crt"
 
 kotlin {
     sourceSets {
-        jvmMain {
+        jvmAndNativeMain {
             dependencies {
                 api(project(":runtime:auth:aws-signing-common"))
                 implementation(project(":runtime:crt-util"))
             }
         }
 
-        jvmTest {
+        jvmAndNativeTest {
             dependencies {
                 implementation(project(":runtime:auth:aws-signing-tests"))
             }
diff --git a/runtime/auth/aws-signing-crt/jvm/src/aws/smithy/kotlin/runtime/auth/awssigning/crt/CrtAwsSigner.kt b/runtime/auth/aws-signing-crt/jvmAndNative/src/aws/smithy/kotlin/runtime/auth/awssigning/crt/CrtAwsSigner.kt
similarity index 100%
rename from runtime/auth/aws-signing-crt/jvm/src/aws/smithy/kotlin/runtime/auth/awssigning/crt/CrtAwsSigner.kt
rename to runtime/auth/aws-signing-crt/jvmAndNative/src/aws/smithy/kotlin/runtime/auth/awssigning/crt/CrtAwsSigner.kt
diff --git a/runtime/auth/aws-signing-crt/jvm/test/aws/smithy/kotlin/runtime/auth/awssigning/crt/CrtAwsChunkedByteReadChannelTest.kt b/runtime/auth/aws-signing-crt/jvmAndNative/test/aws/smithy/kotlin/runtime/auth/awssigning/crt/CrtAwsChunkedByteReadChannelTest.kt
similarity index 100%
rename from runtime/auth/aws-signing-crt/jvm/test/aws/smithy/kotlin/runtime/auth/awssigning/crt/CrtAwsChunkedByteReadChannelTest.kt
rename to runtime/auth/aws-signing-crt/jvmAndNative/test/aws/smithy/kotlin/runtime/auth/awssigning/crt/CrtAwsChunkedByteReadChannelTest.kt
diff --git a/runtime/auth/aws-signing-crt/jvm/test/aws/smithy/kotlin/runtime/auth/awssigning/crt/CrtAwsChunkedSourceTest.kt b/runtime/auth/aws-signing-crt/jvmAndNative/test/aws/smithy/kotlin/runtime/auth/awssigning/crt/CrtAwsChunkedSourceTest.kt
similarity index 100%
rename from runtime/auth/aws-signing-crt/jvm/test/aws/smithy/kotlin/runtime/auth/awssigning/crt/CrtAwsChunkedSourceTest.kt
rename to runtime/auth/aws-signing-crt/jvmAndNative/test/aws/smithy/kotlin/runtime/auth/awssigning/crt/CrtAwsChunkedSourceTest.kt
diff --git a/runtime/auth/aws-signing-crt/jvm/test/aws/smithy/kotlin/runtime/auth/awssigning/crt/CrtBasicSigningTest.kt b/runtime/auth/aws-signing-crt/jvmAndNative/test/aws/smithy/kotlin/runtime/auth/awssigning/crt/CrtBasicSigningTest.kt
similarity index 100%
rename from runtime/auth/aws-signing-crt/jvm/test/aws/smithy/kotlin/runtime/auth/awssigning/crt/CrtBasicSigningTest.kt
rename to runtime/auth/aws-signing-crt/jvmAndNative/test/aws/smithy/kotlin/runtime/auth/awssigning/crt/CrtBasicSigningTest.kt
diff --git a/runtime/auth/aws-signing-crt/jvm/test/aws/smithy/kotlin/runtime/auth/awssigning/crt/CrtSigningSuiteTest.kt b/runtime/auth/aws-signing-crt/jvmAndNative/test/aws/smithy/kotlin/runtime/auth/awssigning/crt/CrtSigningSuiteTest.kt
similarity index 100%
rename from runtime/auth/aws-signing-crt/jvm/test/aws/smithy/kotlin/runtime/auth/awssigning/crt/CrtSigningSuiteTest.kt
rename to runtime/auth/aws-signing-crt/jvmAndNative/test/aws/smithy/kotlin/runtime/auth/awssigning/crt/CrtSigningSuiteTest.kt
diff --git a/runtime/auth/aws-signing-default/jvm/test/aws/smithy/kotlin/runtime/auth/awssigning/DefaultAwsChunkedSourceTest.kt b/runtime/auth/aws-signing-default/common/test/aws/smithy/kotlin/runtime/auth/awssigning/DefaultAwsChunkedSourceTest.kt
similarity index 100%
rename from runtime/auth/aws-signing-default/jvm/test/aws/smithy/kotlin/runtime/auth/awssigning/DefaultAwsChunkedSourceTest.kt
rename to runtime/auth/aws-signing-default/common/test/aws/smithy/kotlin/runtime/auth/awssigning/DefaultAwsChunkedSourceTest.kt
diff --git a/runtime/auth/aws-signing-tests/jvm/src/aws/smithy/kotlin/runtime/auth/awssigning/tests/AwsChunkedSourceTestBase.kt b/runtime/auth/aws-signing-tests/common/src/aws/smithy/kotlin/runtime/auth/awssigning/tests/AwsChunkedSourceTestBase.kt
similarity index 100%
rename from runtime/auth/aws-signing-tests/jvm/src/aws/smithy/kotlin/runtime/auth/awssigning/tests/AwsChunkedSourceTestBase.kt
rename to runtime/auth/aws-signing-tests/common/src/aws/smithy/kotlin/runtime/auth/awssigning/tests/AwsChunkedSourceTestBase.kt
diff --git a/runtime/auth/http-auth-aws/build.gradle.kts b/runtime/auth/http-auth-aws/build.gradle.kts
index dfcc0c7da..e6c823652 100644
--- a/runtime/auth/http-auth-aws/build.gradle.kts
+++ b/runtime/auth/http-auth-aws/build.gradle.kts
@@ -26,7 +26,7 @@ kotlin {
             }
         }
 
-        jvmTest {
+        jvmAndNativeTest {
             dependencies {
                 implementation(project(":runtime:auth:aws-signing-crt"))
             }
diff --git a/runtime/auth/http-auth-aws/jvm/test/AwsHttpSignerTestBaseJvm.kt b/runtime/auth/http-auth-aws/jvmAndNative/test/AwsHttpSignerTestBaseJvmAndNative.kt
similarity index 100%
rename from runtime/auth/http-auth-aws/jvm/test/AwsHttpSignerTestBaseJvm.kt
rename to runtime/auth/http-auth-aws/jvmAndNative/test/AwsHttpSignerTestBaseJvmAndNative.kt
diff --git a/runtime/build.gradle.kts b/runtime/build.gradle.kts
index d02316058..0d1f151e3 100644
--- a/runtime/build.gradle.kts
+++ b/runtime/build.gradle.kts
@@ -14,6 +14,9 @@ plugins {
 
 val sdkVersion: String by project
 
+// Apply KMP configuration from build plugin
+configureKmpTargets()
+
 // capture locally - scope issue with custom KMP plugin
 val libraries = libs
 
@@ -60,7 +63,7 @@ subprojects {
     kotlin.sourceSets.all {
         // Allow subprojects to use internal APIs
         // See https://kotlinlang.org/docs/reference/opt-in-requirements.html#opting-in-to-using-api
-        listOf("kotlin.RequiresOptIn").forEach { languageSettings.optIn(it) }
+        listOf("kotlin.RequiresOptIn", "kotlinx.cinterop.ExperimentalForeignApi").forEach { languageSettings.optIn(it) }
     }
 
     dependencies {
diff --git a/runtime/crt-util/build.gradle.kts b/runtime/crt-util/build.gradle.kts
index ddc57d11a..f14fb5c43 100644
--- a/runtime/crt-util/build.gradle.kts
+++ b/runtime/crt-util/build.gradle.kts
@@ -11,14 +11,22 @@ extra["moduleName"] = "aws.smithy.kotlin.runtime.crt"
 
 kotlin {
     sourceSets {
-        jvmMain {
+        commonMain {
+            dependencies {
+                api(project(":runtime:runtime-core"))
+                api(libs.crt.kotlin)
+            }
+        }
+
+        jvmAndNativeMain {
             dependencies {
                 api(project(":runtime:runtime-core"))
                 api(libs.crt.kotlin)
                 api(project(":runtime:protocol:http"))
             }
         }
-        jvmTest {
+
+        jvmAndNativeTest {
             dependencies {
                 implementation(libs.kotlinx.coroutines.test)
             }
diff --git a/runtime/crt-util/common/src/aws/smithy/kotlin/runtime/crt/ReadChannelBodyStream.kt b/runtime/crt-util/common/src/aws/smithy/kotlin/runtime/crt/ReadChannelBodyStream.kt
new file mode 100644
index 000000000..e08f9f0d1
--- /dev/null
+++ b/runtime/crt-util/common/src/aws/smithy/kotlin/runtime/crt/ReadChannelBodyStream.kt
@@ -0,0 +1,14 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package aws.smithy.kotlin.runtime.crt
+
+import aws.sdk.kotlin.crt.io.MutableBuffer
+import aws.smithy.kotlin.runtime.io.SdkBuffer
+
+/**
+ * write as much of [outgoing] to [dest] as possible
+ */
+internal expect fun transferRequestBody(outgoing: SdkBuffer, dest: MutableBuffer): Int
diff --git a/runtime/crt-util/jvm/src/aws/smithy/kotlin/runtime/crt/ReadChannelBodyStreamJvm.kt b/runtime/crt-util/jvm/src/aws/smithy/kotlin/runtime/crt/ReadChannelBodyStreamJvm.kt
new file mode 100644
index 000000000..7703ef589
--- /dev/null
+++ b/runtime/crt-util/jvm/src/aws/smithy/kotlin/runtime/crt/ReadChannelBodyStreamJvm.kt
@@ -0,0 +1,11 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package aws.smithy.kotlin.runtime.crt
+
+import aws.sdk.kotlin.crt.io.MutableBuffer
+import aws.smithy.kotlin.runtime.io.SdkBuffer
+
+internal actual fun transferRequestBody(outgoing: SdkBuffer, dest: MutableBuffer) = outgoing.read(dest.buffer)
diff --git a/runtime/crt-util/jvm/src/aws/smithy/kotlin/runtime/crt/Http.kt b/runtime/crt-util/jvmAndNative/src/aws/smithy/kotlin/runtime/crt/Http.kt
similarity index 100%
rename from runtime/crt-util/jvm/src/aws/smithy/kotlin/runtime/crt/Http.kt
rename to runtime/crt-util/jvmAndNative/src/aws/smithy/kotlin/runtime/crt/Http.kt
diff --git a/runtime/crt-util/jvm/src/aws/smithy/kotlin/runtime/crt/ReadChannelBodyStream.kt b/runtime/crt-util/jvmAndNative/src/aws/smithy/kotlin/runtime/crt/ReadChannelBodyStream.kt
similarity index 96%
rename from runtime/crt-util/jvm/src/aws/smithy/kotlin/runtime/crt/ReadChannelBodyStream.kt
rename to runtime/crt-util/jvmAndNative/src/aws/smithy/kotlin/runtime/crt/ReadChannelBodyStream.kt
index 4a3e60980..040ba8545 100644
--- a/runtime/crt-util/jvm/src/aws/smithy/kotlin/runtime/crt/ReadChannelBodyStream.kt
+++ b/runtime/crt-util/jvmAndNative/src/aws/smithy/kotlin/runtime/crt/ReadChannelBodyStream.kt
@@ -18,11 +18,6 @@ import kotlin.time.Duration.Companion.milliseconds
 
 private val POLLING_DELAY = 100.milliseconds
 
-/**
- * write as much of [outgoing] to [dest] as possible
- */
-internal fun transferRequestBody(outgoing: SdkBuffer, dest: MutableBuffer) = outgoing.read(dest.buffer)
-
 /**
  * Implement's [HttpRequestBodyStream] which proxies an SDK request body channel [SdkByteReadChannel]
  */
diff --git a/runtime/crt-util/jvm/src/aws/smithy/kotlin/runtime/crt/SdkDefaultIO.kt b/runtime/crt-util/jvmAndNative/src/aws/smithy/kotlin/runtime/crt/SdkDefaultIO.kt
similarity index 100%
rename from runtime/crt-util/jvm/src/aws/smithy/kotlin/runtime/crt/SdkDefaultIO.kt
rename to runtime/crt-util/jvmAndNative/src/aws/smithy/kotlin/runtime/crt/SdkDefaultIO.kt
diff --git a/runtime/crt-util/jvm/src/aws/smithy/kotlin/runtime/crt/SdkSourceBodyStream.kt b/runtime/crt-util/jvmAndNative/src/aws/smithy/kotlin/runtime/crt/SdkSourceBodyStream.kt
similarity index 100%
rename from runtime/crt-util/jvm/src/aws/smithy/kotlin/runtime/crt/SdkSourceBodyStream.kt
rename to runtime/crt-util/jvmAndNative/src/aws/smithy/kotlin/runtime/crt/SdkSourceBodyStream.kt
diff --git a/runtime/crt-util/jvm/test/aws/smithy/kotlin/runtime/crt/HttpTest.kt b/runtime/crt-util/jvmAndNative/test/aws/smithy/kotlin/runtime/crt/HttpTest.kt
similarity index 100%
rename from runtime/crt-util/jvm/test/aws/smithy/kotlin/runtime/crt/HttpTest.kt
rename to runtime/crt-util/jvmAndNative/test/aws/smithy/kotlin/runtime/crt/HttpTest.kt
diff --git a/runtime/crt-util/jvm/test/aws/smithy/kotlin/runtime/crt/ReadChannelBodyStreamTest.kt b/runtime/crt-util/jvmAndNative/test/aws/smithy/kotlin/runtime/crt/ReadChannelBodyStreamTest.kt
similarity index 100%
rename from runtime/crt-util/jvm/test/aws/smithy/kotlin/runtime/crt/ReadChannelBodyStreamTest.kt
rename to runtime/crt-util/jvmAndNative/test/aws/smithy/kotlin/runtime/crt/ReadChannelBodyStreamTest.kt
diff --git a/runtime/crt-util/jvm/test/aws/smithy/kotlin/runtime/crt/SdkSourceBodyStreamTest.kt b/runtime/crt-util/jvmAndNative/test/aws/smithy/kotlin/runtime/crt/SdkSourceBodyStreamTest.kt
similarity index 100%
rename from runtime/crt-util/jvm/test/aws/smithy/kotlin/runtime/crt/SdkSourceBodyStreamTest.kt
rename to runtime/crt-util/jvmAndNative/test/aws/smithy/kotlin/runtime/crt/SdkSourceBodyStreamTest.kt
diff --git a/runtime/crt-util/native/src/aws/smithy/kotlin/runtime/crt/ReadChannelBodyStreamNative.kt b/runtime/crt-util/native/src/aws/smithy/kotlin/runtime/crt/ReadChannelBodyStreamNative.kt
new file mode 100644
index 000000000..09eb88dfd
--- /dev/null
+++ b/runtime/crt-util/native/src/aws/smithy/kotlin/runtime/crt/ReadChannelBodyStreamNative.kt
@@ -0,0 +1,10 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package aws.smithy.kotlin.runtime.crt
+
+import aws.sdk.kotlin.crt.io.MutableBuffer
+import aws.smithy.kotlin.runtime.io.SdkBuffer
+
+internal actual fun transferRequestBody(outgoing: SdkBuffer, dest: MutableBuffer): Int = TODO("Not yet implemented")
diff --git a/runtime/observability/telemetry-api/jvm/src/aws/smithy/kotlin/runtime/telemetry/context/TelemetryContextElementJVM.kt b/runtime/observability/telemetry-api/jvm/src/aws/smithy/kotlin/runtime/telemetry/context/TelemetryContextElementJVM.kt
index d6680f0d6..e8548ad31 100644
--- a/runtime/observability/telemetry-api/jvm/src/aws/smithy/kotlin/runtime/telemetry/context/TelemetryContextElementJVM.kt
+++ b/runtime/observability/telemetry-api/jvm/src/aws/smithy/kotlin/runtime/telemetry/context/TelemetryContextElementJVM.kt
@@ -10,6 +10,7 @@ import kotlinx.coroutines.ThreadContextElement
 import kotlin.coroutines.AbstractCoroutineContextElement
 import kotlin.coroutines.CoroutineContext
 
+// FIXME Move to jvmAndNative when https://github.com/Kotlin/kotlinx.coroutines/issues/3326 is implemented
 @InternalApi
 public actual class TelemetryContextElement public actual constructor(
     public actual val context: Context,
diff --git a/runtime/protocol/http-client-engines/http-client-engine-crt/build.gradle.kts b/runtime/protocol/http-client-engines/http-client-engine-crt/build.gradle.kts
index d2f411578..b3a3f5507 100644
--- a/runtime/protocol/http-client-engines/http-client-engine-crt/build.gradle.kts
+++ b/runtime/protocol/http-client-engines/http-client-engine-crt/build.gradle.kts
@@ -11,18 +11,18 @@ apply(plugin = "org.jetbrains.kotlinx.atomicfu")
 
 kotlin {
     sourceSets {
-        jvmMain {
+        jvmAndNativeMain {
             dependencies {
                 api(project(":runtime:runtime-core"))
                 api(project(":runtime:protocol:http-client"))
                 implementation(project(":runtime:crt-util"))
                 implementation(project(":runtime:observability:telemetry-api"))
-
                 implementation(libs.kotlinx.coroutines.core)
+                api(libs.crt.kotlin)
             }
         }
 
-        jvmTest {
+        jvmAndNativeTest {
             dependencies {
                 implementation(project(":runtime:testing"))
                 implementation(project(":runtime:protocol:http-test"))
diff --git a/runtime/protocol/http-client-engines/http-client-engine-crt/jvm/src/aws/smithy/kotlin/runtime/http/engine/crt/ConnectionManager.kt b/runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/src/aws/smithy/kotlin/runtime/http/engine/crt/ConnectionManager.kt
similarity index 100%
rename from runtime/protocol/http-client-engines/http-client-engine-crt/jvm/src/aws/smithy/kotlin/runtime/http/engine/crt/ConnectionManager.kt
rename to runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/src/aws/smithy/kotlin/runtime/http/engine/crt/ConnectionManager.kt
diff --git a/runtime/protocol/http-client-engines/http-client-engine-crt/jvm/src/aws/smithy/kotlin/runtime/http/engine/crt/CrtHttpEngine.kt b/runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/src/aws/smithy/kotlin/runtime/http/engine/crt/CrtHttpEngine.kt
similarity index 100%
rename from runtime/protocol/http-client-engines/http-client-engine-crt/jvm/src/aws/smithy/kotlin/runtime/http/engine/crt/CrtHttpEngine.kt
rename to runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/src/aws/smithy/kotlin/runtime/http/engine/crt/CrtHttpEngine.kt
diff --git a/runtime/protocol/http-client-engines/http-client-engine-crt/jvm/src/aws/smithy/kotlin/runtime/http/engine/crt/CrtHttpEngineConfig.kt b/runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/src/aws/smithy/kotlin/runtime/http/engine/crt/CrtHttpEngineConfig.kt
similarity index 100%
rename from runtime/protocol/http-client-engines/http-client-engine-crt/jvm/src/aws/smithy/kotlin/runtime/http/engine/crt/CrtHttpEngineConfig.kt
rename to runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/src/aws/smithy/kotlin/runtime/http/engine/crt/CrtHttpEngineConfig.kt
diff --git a/runtime/protocol/http-client-engines/http-client-engine-crt/jvm/src/aws/smithy/kotlin/runtime/http/engine/crt/RequestUtil.kt b/runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/src/aws/smithy/kotlin/runtime/http/engine/crt/RequestUtil.kt
similarity index 100%
rename from runtime/protocol/http-client-engines/http-client-engine-crt/jvm/src/aws/smithy/kotlin/runtime/http/engine/crt/RequestUtil.kt
rename to runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/src/aws/smithy/kotlin/runtime/http/engine/crt/RequestUtil.kt
diff --git a/runtime/protocol/http-client-engines/http-client-engine-crt/jvm/src/aws/smithy/kotlin/runtime/http/engine/crt/SdkStreamResponseHandler.kt b/runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/src/aws/smithy/kotlin/runtime/http/engine/crt/SdkStreamResponseHandler.kt
similarity index 100%
rename from runtime/protocol/http-client-engines/http-client-engine-crt/jvm/src/aws/smithy/kotlin/runtime/http/engine/crt/SdkStreamResponseHandler.kt
rename to runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/src/aws/smithy/kotlin/runtime/http/engine/crt/SdkStreamResponseHandler.kt
diff --git a/runtime/protocol/http-client-engines/http-client-engine-crt/jvm/test/aws/smithy/kotlin/runtime/http/engine/crt/AsyncStressTest.kt b/runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/test/aws/smithy/kotlin/runtime/http/engine/crt/AsyncStressTest.kt
similarity index 97%
rename from runtime/protocol/http-client-engines/http-client-engine-crt/jvm/test/aws/smithy/kotlin/runtime/http/engine/crt/AsyncStressTest.kt
rename to runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/test/aws/smithy/kotlin/runtime/http/engine/crt/AsyncStressTest.kt
index 7ad57fa1a..96efc44f7 100644
--- a/runtime/protocol/http-client-engines/http-client-engine-crt/jvm/test/aws/smithy/kotlin/runtime/http/engine/crt/AsyncStressTest.kt
+++ b/runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/test/aws/smithy/kotlin/runtime/http/engine/crt/AsyncStressTest.kt
@@ -25,6 +25,7 @@ import kotlinx.coroutines.yield
 import kotlin.test.Test
 import kotlin.time.Duration.Companion.seconds
 
+// FIXME This test implements [TestWithLocalServer] which is JVM-only.
 class AsyncStressTest : TestWithLocalServer() {
 
     override val server = embeddedServer(CIO, serverPort) {
diff --git a/runtime/protocol/http-client-engines/http-client-engine-crt/jvm/test/aws/smithy/kotlin/runtime/http/engine/crt/RequestConversionTest.kt b/runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/test/aws/smithy/kotlin/runtime/http/engine/crt/RequestConversionTest.kt
similarity index 100%
rename from runtime/protocol/http-client-engines/http-client-engine-crt/jvm/test/aws/smithy/kotlin/runtime/http/engine/crt/RequestConversionTest.kt
rename to runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/test/aws/smithy/kotlin/runtime/http/engine/crt/RequestConversionTest.kt
diff --git a/runtime/protocol/http-client-engines/http-client-engine-crt/jvm/test/aws/smithy/kotlin/runtime/http/engine/crt/RequestUtilTest.kt b/runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/test/aws/smithy/kotlin/runtime/http/engine/crt/RequestUtilTest.kt
similarity index 100%
rename from runtime/protocol/http-client-engines/http-client-engine-crt/jvm/test/aws/smithy/kotlin/runtime/http/engine/crt/RequestUtilTest.kt
rename to runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/test/aws/smithy/kotlin/runtime/http/engine/crt/RequestUtilTest.kt
diff --git a/runtime/protocol/http-client-engines/http-client-engine-crt/jvm/test/aws/smithy/kotlin/runtime/http/engine/crt/SdkStreamResponseHandlerTest.kt b/runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/test/aws/smithy/kotlin/runtime/http/engine/crt/SdkStreamResponseHandlerTest.kt
similarity index 97%
rename from runtime/protocol/http-client-engines/http-client-engine-crt/jvm/test/aws/smithy/kotlin/runtime/http/engine/crt/SdkStreamResponseHandlerTest.kt
rename to runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/test/aws/smithy/kotlin/runtime/http/engine/crt/SdkStreamResponseHandlerTest.kt
index 9bbc35c4c..005d577f7 100644
--- a/runtime/protocol/http-client-engines/http-client-engine-crt/jvm/test/aws/smithy/kotlin/runtime/http/engine/crt/SdkStreamResponseHandlerTest.kt
+++ b/runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/test/aws/smithy/kotlin/runtime/http/engine/crt/SdkStreamResponseHandlerTest.kt
@@ -21,15 +21,17 @@ import kotlinx.coroutines.yield
 import kotlin.test.*
 
 class SdkStreamResponseHandlerTest {
-
     private class MockHttpStream(override val responseStatusCode: Int) : HttpStream {
         var closed: Boolean = false
         override fun activate() {}
+        override suspend fun writeChunk(chunkData: ByteArray, isFinalChunk: Boolean) {
+            TODO("Not yet implemented")
+        }
+
         override fun close() {
             closed = true
         }
         override fun incrementWindow(size: Int) {}
-        override fun writeChunk(chunkData: ByteArray, isFinalChunk: Boolean) {}
     }
 
     private class MockHttpClientConnection : HttpClientConnection {
diff --git a/runtime/protocol/http-client-engines/http-client-engine-crt/jvm/test/aws/smithy/kotlin/runtime/http/engine/crt/SendChunkedBodyTest.kt b/runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/test/aws/smithy/kotlin/runtime/http/engine/crt/SendChunkedBodyTest.kt
similarity index 97%
rename from runtime/protocol/http-client-engines/http-client-engine-crt/jvm/test/aws/smithy/kotlin/runtime/http/engine/crt/SendChunkedBodyTest.kt
rename to runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/test/aws/smithy/kotlin/runtime/http/engine/crt/SendChunkedBodyTest.kt
index a7637b675..d0e2e2cf9 100644
--- a/runtime/protocol/http-client-engines/http-client-engine-crt/jvm/test/aws/smithy/kotlin/runtime/http/engine/crt/SendChunkedBodyTest.kt
+++ b/runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/test/aws/smithy/kotlin/runtime/http/engine/crt/SendChunkedBodyTest.kt
@@ -22,7 +22,7 @@ class SendChunkedBodyTest {
             closed = true
         }
         override fun incrementWindow(size: Int) {}
-        override fun writeChunk(chunkData: ByteArray, isFinalChunk: Boolean) {
+        override suspend fun writeChunk(chunkData: ByteArray, isFinalChunk: Boolean) {
             numChunksWritten += 1
         }
     }
diff --git a/runtime/protocol/http-client-engines/http-client-engine-okhttp/build.gradle.kts b/runtime/protocol/http-client-engines/http-client-engine-okhttp/build.gradle.kts
index 3e5d13938..0e12749c0 100644
--- a/runtime/protocol/http-client-engines/http-client-engine-okhttp/build.gradle.kts
+++ b/runtime/protocol/http-client-engines/http-client-engine-okhttp/build.gradle.kts
@@ -9,7 +9,7 @@ extra["moduleName"] = "aws.smithy.kotlin.runtime.http.engine.okhttp"
 
 kotlin {
     sourceSets {
-        commonMain {
+        jvmMain {
             dependencies {
                 implementation(project(":runtime:runtime-core"))
                 api(project(":runtime:protocol:http-client"))
diff --git a/runtime/protocol/http-client-engines/http-client-engine-okhttp4/build.gradle.kts b/runtime/protocol/http-client-engines/http-client-engine-okhttp4/build.gradle.kts
index 26145b406..f6b3f1266 100644
--- a/runtime/protocol/http-client-engines/http-client-engine-okhttp4/build.gradle.kts
+++ b/runtime/protocol/http-client-engines/http-client-engine-okhttp4/build.gradle.kts
@@ -9,7 +9,7 @@ extra["moduleName"] = "aws.smithy.kotlin.runtime.http.engine.okhttp4"
 
 kotlin {
     sourceSets {
-        commonMain {
+        jvmMain {
             dependencies {
                 api(project(":runtime:protocol:http-client"))
                 implementation(project(":runtime:protocol:http-client-engines:http-client-engine-okhttp"))
diff --git a/runtime/protocol/http-client-engines/test-suite/build.gradle.kts b/runtime/protocol/http-client-engines/test-suite/build.gradle.kts
index ece9d6e10..065872fe7 100644
--- a/runtime/protocol/http-client-engines/test-suite/build.gradle.kts
+++ b/runtime/protocol/http-client-engines/test-suite/build.gradle.kts
@@ -38,6 +38,7 @@ kotlin {
 
         jvmAndNativeMain {
             dependencies {
+                implementation(libs.ktor.server.core)
                 implementation(libs.kotlinx.coroutines.test)
             }
         }
diff --git a/runtime/protocol/http-client-engines/test-suite/jvm/src/aws/smithy/kotlin/runtime/http/test/util/AbstractEngineTestJVM.kt b/runtime/protocol/http-client-engines/test-suite/jvm/src/aws/smithy/kotlin/runtime/http/test/util/AbstractEngineTestJVM.kt
index fa091c1f0..6f0d9182d 100644
--- a/runtime/protocol/http-client-engines/test-suite/jvm/src/aws/smithy/kotlin/runtime/http/test/util/AbstractEngineTestJVM.kt
+++ b/runtime/protocol/http-client-engines/test-suite/jvm/src/aws/smithy/kotlin/runtime/http/test/util/AbstractEngineTestJVM.kt
@@ -11,6 +11,7 @@ import aws.smithy.kotlin.runtime.http.engine.okhttp4.OkHttp4Engine
 import aws.smithy.kotlin.runtime.net.url.Url
 
 internal actual fun engineFactories(): List<TestEngineFactory> =
+    // FIXME Move DefaultHttpEngine and CrtHttpEngine to `jvmAndNative`
     listOf(
         TestEngineFactory("DefaultHttpEngine", ::DefaultHttpEngine),
         TestEngineFactory("CrtHttpEngine") { CrtHttpEngine(it) },
diff --git a/runtime/protocol/http-client-engines/test-suite/jvm/src/aws/smithy/kotlin/runtime/http/test/util/TestServers.kt b/runtime/protocol/http-client-engines/test-suite/jvm/src/aws/smithy/kotlin/runtime/http/test/util/TestServers.kt
index 1bc9d6e9e..24c001d5b 100644
--- a/runtime/protocol/http-client-engines/test-suite/jvm/src/aws/smithy/kotlin/runtime/http/test/util/TestServers.kt
+++ b/runtime/protocol/http-client-engines/test-suite/jvm/src/aws/smithy/kotlin/runtime/http/test/util/TestServers.kt
@@ -12,7 +12,6 @@ import aws.smithy.kotlin.runtime.http.test.suite.tlsTests
 import aws.smithy.kotlin.runtime.http.test.suite.uploadTests
 import io.ktor.server.application.*
 import io.ktor.server.engine.*
-import io.ktor.server.jetty.*
 import io.ktor.server.jetty.jakarta.Jetty
 import io.ktor.server.jetty.jakarta.JettyApplicationEngineBase
 import redirectTests
diff --git a/runtime/protocol/http-client-engines/test-suite/jvm/src/aws/smithy/kotlin/runtime/http/test/suite/Concurrency.kt b/runtime/protocol/http-client-engines/test-suite/jvmAndNative/src/aws/smithy/kotlin/runtime/http/test/suite/Concurrency.kt
similarity index 88%
rename from runtime/protocol/http-client-engines/test-suite/jvm/src/aws/smithy/kotlin/runtime/http/test/suite/Concurrency.kt
rename to runtime/protocol/http-client-engines/test-suite/jvmAndNative/src/aws/smithy/kotlin/runtime/http/test/suite/Concurrency.kt
index fad3e7fec..b3b482fa2 100644
--- a/runtime/protocol/http-client-engines/test-suite/jvm/src/aws/smithy/kotlin/runtime/http/test/suite/Concurrency.kt
+++ b/runtime/protocol/http-client-engines/test-suite/jvmAndNative/src/aws/smithy/kotlin/runtime/http/test/suite/Concurrency.kt
@@ -8,6 +8,7 @@ package aws.smithy.kotlin.runtime.http.test.suite
 import io.ktor.server.application.*
 import io.ktor.server.response.*
 import io.ktor.server.routing.*
+import io.ktor.utils.io.writeFully
 import kotlinx.coroutines.delay
 import kotlin.time.Duration.Companion.milliseconds
 
@@ -24,10 +25,10 @@ internal fun Application.concurrentTests() {
         route("slow") {
             get {
                 val chunk = ByteArray(256) { it.toByte() }
-                call.respondOutputStream {
+                call.respondBytesWriter {
                     repeat(10) {
                         delay(200.milliseconds)
-                        write(chunk)
+                        writeFully(chunk)
                     }
                 }
             }
diff --git a/runtime/protocol/http-client-engines/test-suite/jvm/src/aws/smithy/kotlin/runtime/http/test/suite/Connections.kt b/runtime/protocol/http-client-engines/test-suite/jvmAndNative/src/aws/smithy/kotlin/runtime/http/test/suite/Connections.kt
similarity index 100%
rename from runtime/protocol/http-client-engines/test-suite/jvm/src/aws/smithy/kotlin/runtime/http/test/suite/Connections.kt
rename to runtime/protocol/http-client-engines/test-suite/jvmAndNative/src/aws/smithy/kotlin/runtime/http/test/suite/Connections.kt
diff --git a/runtime/protocol/http-client-engines/test-suite/jvm/src/aws/smithy/kotlin/runtime/http/test/suite/Downloads.kt b/runtime/protocol/http-client-engines/test-suite/jvmAndNative/src/aws/smithy/kotlin/runtime/http/test/suite/Downloads.kt
similarity index 84%
rename from runtime/protocol/http-client-engines/test-suite/jvm/src/aws/smithy/kotlin/runtime/http/test/suite/Downloads.kt
rename to runtime/protocol/http-client-engines/test-suite/jvmAndNative/src/aws/smithy/kotlin/runtime/http/test/suite/Downloads.kt
index dd495edf2..7cd8ba93e 100644
--- a/runtime/protocol/http-client-engines/test-suite/jvm/src/aws/smithy/kotlin/runtime/http/test/suite/Downloads.kt
+++ b/runtime/protocol/http-client-engines/test-suite/jvmAndNative/src/aws/smithy/kotlin/runtime/http/test/suite/Downloads.kt
@@ -6,6 +6,9 @@
 package aws.smithy.kotlin.runtime.http.test.suite
 
 import aws.smithy.kotlin.runtime.hashing.sha256
+import aws.smithy.kotlin.runtime.io.GzipSdkSource
+import aws.smithy.kotlin.runtime.io.readToByteArray
+import aws.smithy.kotlin.runtime.io.source
 import aws.smithy.kotlin.runtime.text.encoding.encodeToHex
 import io.ktor.http.*
 import io.ktor.server.application.*
@@ -13,8 +16,6 @@ import io.ktor.server.response.*
 import io.ktor.server.routing.*
 import io.ktor.utils.io.*
 import kotlinx.coroutines.delay
-import java.io.ByteArrayOutputStream
-import java.util.zip.GZIPOutputStream
 import kotlin.random.Random
 
 internal const val DOWNLOAD_SIZE = 16L * 1024 * 1024 // 16MB
@@ -55,15 +56,7 @@ internal fun Application.downloadTests() {
 
             get("/gzipped") {
                 val uncompressed = ByteArray(1024) { it.toByte() }
-                val compressed = ByteArrayOutputStream().use { baStream ->
-                    GZIPOutputStream(baStream).use { gzStream ->
-                        gzStream.write(uncompressed)
-                        gzStream.flush()
-                    }
-                    baStream.flush()
-                    baStream.toByteArray()
-                }
-
+                val compressed = GzipSdkSource(uncompressed.source()).readToByteArray()
                 call.response.header("Content-Encoding", "gzip")
                 call.respondBytes(compressed)
             }
diff --git a/runtime/protocol/http-client-engines/test-suite/jvm/src/aws/smithy/kotlin/runtime/http/test/suite/Header.kt b/runtime/protocol/http-client-engines/test-suite/jvmAndNative/src/aws/smithy/kotlin/runtime/http/test/suite/Header.kt
similarity index 100%
rename from runtime/protocol/http-client-engines/test-suite/jvm/src/aws/smithy/kotlin/runtime/http/test/suite/Header.kt
rename to runtime/protocol/http-client-engines/test-suite/jvmAndNative/src/aws/smithy/kotlin/runtime/http/test/suite/Header.kt
diff --git a/runtime/protocol/http-client-engines/test-suite/jvm/src/aws/smithy/kotlin/runtime/http/test/suite/Redirects.kt b/runtime/protocol/http-client-engines/test-suite/jvmAndNative/src/aws/smithy/kotlin/runtime/http/test/suite/Redirects.kt
similarity index 100%
rename from runtime/protocol/http-client-engines/test-suite/jvm/src/aws/smithy/kotlin/runtime/http/test/suite/Redirects.kt
rename to runtime/protocol/http-client-engines/test-suite/jvmAndNative/src/aws/smithy/kotlin/runtime/http/test/suite/Redirects.kt
diff --git a/runtime/protocol/http-client-engines/test-suite/jvm/src/aws/smithy/kotlin/runtime/http/test/suite/Tls.kt b/runtime/protocol/http-client-engines/test-suite/jvmAndNative/src/aws/smithy/kotlin/runtime/http/test/suite/Tls.kt
similarity index 100%
rename from runtime/protocol/http-client-engines/test-suite/jvm/src/aws/smithy/kotlin/runtime/http/test/suite/Tls.kt
rename to runtime/protocol/http-client-engines/test-suite/jvmAndNative/src/aws/smithy/kotlin/runtime/http/test/suite/Tls.kt
diff --git a/runtime/protocol/http-client-engines/test-suite/jvm/src/aws/smithy/kotlin/runtime/http/test/suite/Uploads.kt b/runtime/protocol/http-client-engines/test-suite/jvmAndNative/src/aws/smithy/kotlin/runtime/http/test/suite/Uploads.kt
similarity index 100%
rename from runtime/protocol/http-client-engines/test-suite/jvm/src/aws/smithy/kotlin/runtime/http/test/suite/Uploads.kt
rename to runtime/protocol/http-client-engines/test-suite/jvmAndNative/src/aws/smithy/kotlin/runtime/http/test/suite/Uploads.kt
diff --git a/runtime/protocol/http-client-engines/test-suite/native/src/aws/smithy/kotlin/runtime/http/test/util/AbstractEngineTestNative.kt b/runtime/protocol/http-client-engines/test-suite/native/src/aws/smithy/kotlin/runtime/http/test/util/AbstractEngineTestNative.kt
index bfb3ff18f..05f82f63d 100644
--- a/runtime/protocol/http-client-engines/test-suite/native/src/aws/smithy/kotlin/runtime/http/test/util/AbstractEngineTestNative.kt
+++ b/runtime/protocol/http-client-engines/test-suite/native/src/aws/smithy/kotlin/runtime/http/test/util/AbstractEngineTestNative.kt
@@ -7,7 +7,7 @@ package aws.smithy.kotlin.runtime.http.test.util
 
 import aws.smithy.kotlin.runtime.net.url.Url
 
-// FIXME add engines to test
+// FIXME Move CRT and Default engine tests to `jvmAndNative`
 internal actual fun engineFactories(): List<TestEngineFactory> =
     listOf()
 
diff --git a/runtime/protocol/http-client/native/test/aws/smithy/kotlin/runtime/http/interceptors/RequestCompressionInterceptorTestNative.kt b/runtime/protocol/http-client/native/test/aws/smithy/kotlin/runtime/http/interceptors/RequestCompressionInterceptorTestNative.kt
index 74cbd525c..7d55f1834 100644
--- a/runtime/protocol/http-client/native/test/aws/smithy/kotlin/runtime/http/interceptors/RequestCompressionInterceptorTestNative.kt
+++ b/runtime/protocol/http-client/native/test/aws/smithy/kotlin/runtime/http/interceptors/RequestCompressionInterceptorTestNative.kt
@@ -5,5 +5,5 @@
 package aws.smithy.kotlin.runtime.http.interceptors
 
 internal actual fun decompressGzipBytes(bytes: ByteArray): ByteArray {
-    TODO("Not yet implemented")
+    TODO("Not yet implemented. Can we write a pure Kotlin implementation?")
 }
diff --git a/runtime/runtime-core/common/test/aws/smithy/kotlin/runtime/io/GzipTestUtils.kt b/runtime/runtime-core/common/test/aws/smithy/kotlin/runtime/io/GzipTestUtils.kt
index 109844814..511fe59f4 100644
--- a/runtime/runtime-core/common/test/aws/smithy/kotlin/runtime/io/GzipTestUtils.kt
+++ b/runtime/runtime-core/common/test/aws/smithy/kotlin/runtime/io/GzipTestUtils.kt
@@ -5,6 +5,6 @@
 package aws.smithy.kotlin.runtime.io
 
 /**
- * Decompresses a byte array compressed using the gzip format
+ * Decompresses a [ByteArray] compressed using the gzip format
  */
 internal expect fun decompressGzipBytes(bytes: ByteArray): ByteArray
diff --git a/runtime/runtime-core/jvm/src/aws/smithy/kotlin/runtime/io/SdkByteReadChannelJVM.kt b/runtime/runtime-core/jvm/src/aws/smithy/kotlin/runtime/io/SdkByteReadChannelJVM.kt
index 5afef0174..2986b998a 100644
--- a/runtime/runtime-core/jvm/src/aws/smithy/kotlin/runtime/io/SdkByteReadChannelJVM.kt
+++ b/runtime/runtime-core/jvm/src/aws/smithy/kotlin/runtime/io/SdkByteReadChannelJVM.kt
@@ -6,7 +6,6 @@ package aws.smithy.kotlin.runtime.io
 
 import kotlinx.coroutines.runBlocking
 import java.io.InputStream
-import java.util.*
 
 /**
  * Create a blocking [InputStream] that blocks everytime the channel suspends at [SdkByteReadChannel.read]
diff --git a/runtime/runtime-core/jvm/src/aws/smithy/kotlin/runtime/time/InstantJVM.kt b/runtime/runtime-core/jvm/src/aws/smithy/kotlin/runtime/time/InstantJVM.kt
index b90a57de8..e1a17cd8c 100644
--- a/runtime/runtime-core/jvm/src/aws/smithy/kotlin/runtime/time/InstantJVM.kt
+++ b/runtime/runtime-core/jvm/src/aws/smithy/kotlin/runtime/time/InstantJVM.kt
@@ -26,6 +26,7 @@ import kotlin.time.toKotlinDuration
 import java.time.Duration as jtDuration
 import java.time.Instant as jtInstant
 
+// FIXME Consider making this multiplatform (`common`) using kotlinx.datetime
 public actual class Instant(internal val value: jtInstant) : Comparable<Instant> {
     public actual val epochSeconds: Long
         get() = value.epochSecond
diff --git a/runtime/runtime-core/jvm/test/aws/smithy/kotlin/runtime/io/GzipTestUtilsJVM.kt b/runtime/runtime-core/jvm/test/aws/smithy/kotlin/runtime/io/GzipTestUtilsJVM.kt
index 1d79af810..1d879aa92 100644
--- a/runtime/runtime-core/jvm/test/aws/smithy/kotlin/runtime/io/GzipTestUtilsJVM.kt
+++ b/runtime/runtime-core/jvm/test/aws/smithy/kotlin/runtime/io/GzipTestUtilsJVM.kt
@@ -7,7 +7,7 @@ package aws.smithy.kotlin.runtime.io
 import java.util.zip.GZIPInputStream
 
 /**
- * Decompresses a byte array compressed using the gzip format
+ * Decompresses a [ByteArray] compressed using the gzip format
  */
 internal actual fun decompressGzipBytes(bytes: ByteArray): ByteArray =
     GZIPInputStream(bytes.inputStream()).use { it.readBytes() }
diff --git a/runtime/runtime-core/native/src/aws/smithy/kotlin/runtime/time/InstantNative.kt b/runtime/runtime-core/native/src/aws/smithy/kotlin/runtime/time/InstantNative.kt
index 00bc92f2f..56e4b8d3b 100644
--- a/runtime/runtime-core/native/src/aws/smithy/kotlin/runtime/time/InstantNative.kt
+++ b/runtime/runtime-core/native/src/aws/smithy/kotlin/runtime/time/InstantNative.kt
@@ -7,6 +7,7 @@ package aws.smithy.kotlin.runtime.time
 
 import kotlin.time.Duration
 
+// FIXME Consider making this multiplatform (`common`) using kotlinx.datetime
 public actual class Instant : Comparable<Instant> {
     actual override fun compareTo(other: Instant): Int {
         TODO("Not yet implemented")
diff --git a/settings.gradle.kts b/settings.gradle.kts
index 414df686a..ac7f398bc 100644
--- a/settings.gradle.kts
+++ b/settings.gradle.kts
@@ -26,6 +26,39 @@ dependencyResolutionManagement {
     }
 }
 
+// Set up a sibling directory aws-crt-kotlin as a composite build, if it exists.
+// Allows overrides via local.properties:
+// compositeProjects=~/repos/aws-crt-kotlin,/tmp/some/other/thing,../../another/project
+val compositeProjectList = try {
+    val localProperties = java.util.Properties().also {
+        it.load(File(rootProject.projectDir, "local.properties").inputStream())
+    }
+    val compositeProjects = localProperties.getProperty("compositeProjects") ?: "../aws-crt-kotlin"
+
+    val compositeProjectPaths = compositeProjects.split(",")
+        .map { it.replaceFirst("^~".toRegex(), System.getProperty("user.home")) } // expand ~ to user's home directory
+        .filter { it.isNotBlank() }
+        .map { file(it) }
+
+    compositeProjectPaths.also {
+        if (it.isNotEmpty()) {
+            println("Adding composite build projects from local.properties: ${compositeProjectPaths.joinToString { it.name }}")
+        }
+    }
+} catch (e: Throwable) {
+    logger.error("Failed to load composite project paths from local.properties")
+    listOf(file("../aws-crt-kotlin"))
+}
+
+compositeProjectList.forEach {
+    if (it.exists()) {
+        println("Including build '$it'")
+        includeBuild(it)
+    } else {
+        println("Ignoring invalid build directory '$it'")
+    }
+}
+
 rootProject.name = "smithy-kotlin"
 
 include(":dokka-smithy")