diff --git a/.github/workflows/artifact-size-metrics.yml b/.github/workflows/artifact-size-metrics.yml
index a9d3c7b6e9..fb0be57b67 100644
--- a/.github/workflows/artifact-size-metrics.yml
+++ b/.github/workflows/artifact-size-metrics.yml
@@ -45,23 +45,25 @@ jobs:
     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: Setup build
+        uses: .github/actions/setup-build
+
       - name: Configure AWS Credentials
         uses: aws-actions/configure-aws-credentials@v4
         with:
           role-to-assume: ${{ secrets.CI_AWS_ROLE_ARN }}
           aws-region: us-west-2
+
       - name: Configure Gradle
         uses: awslabs/aws-kotlin-repo-tools/.github/actions/configure-gradle@main
+
       - name: Generate Artifact Size Metrics
         run: ./gradlew -Paws.kotlin.native=false artifactSizeMetrics
+
       - name: Analyze Artifact Size Metrics
         run: ./gradlew analyzeArtifactSizeMetrics
+
       - name: Show Results
         uses: actions/github-script@v7
         with:
diff --git a/runtime/auth/aws-signing-crt/api/aws-signing-crt.api b/runtime/auth/aws-signing-crt/api/aws-signing-crt.api
index ed1934cac9..39dc9fdf45 100644
--- a/runtime/auth/aws-signing-crt/api/aws-signing-crt.api
+++ b/runtime/auth/aws-signing-crt/api/aws-signing-crt.api
@@ -1,4 +1,4 @@
-public final class aws/smithy/kotlin/runtime/auth/awssigning/crt/CrtAwsSigner : aws/smithy/kotlin/runtime/auth/awssigning/AwsSigner {
+public final class aws/smithy/kotlin/runtime/auth/awssigning/crt/CrtAwsSigner : aws/sdk/kotlin/crt/WithCrt, aws/smithy/kotlin/runtime/auth/awssigning/AwsSigner {
 	public static final field INSTANCE Laws/smithy/kotlin/runtime/auth/awssigning/crt/CrtAwsSigner;
 	public fun sign (Laws/smithy/kotlin/runtime/http/request/HttpRequest;Laws/smithy/kotlin/runtime/auth/awssigning/AwsSigningConfig;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
 	public fun signChunk ([B[BLaws/smithy/kotlin/runtime/auth/awssigning/AwsSigningConfig;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
diff --git a/runtime/auth/aws-signing-crt/jvmAndNative/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
index c0069c1aca..ac039d519b 100644
--- a/runtime/auth/aws-signing-crt/jvmAndNative/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
@@ -4,6 +4,7 @@
  */
 package aws.smithy.kotlin.runtime.auth.awssigning.crt
 
+import aws.sdk.kotlin.crt.WithCrt
 import aws.smithy.kotlin.runtime.auth.awscredentials.Credentials
 import aws.smithy.kotlin.runtime.auth.awssigning.*
 import aws.smithy.kotlin.runtime.crt.toSignableCrtRequest
@@ -24,7 +25,7 @@ import aws.sdk.kotlin.crt.http.Headers as CrtHeaders
 
 private const val S3_EXPRESS_HEADER_NAME = "X-Amz-S3session-Token"
 
-public object CrtAwsSigner : AwsSigner {
+public object CrtAwsSigner : AwsSigner, WithCrt() {
     override suspend fun sign(request: HttpRequest, config: AwsSigningConfig): AwsSigningResult<HttpRequest> {
         val isUnsigned = config.hashSpecification is HashSpecification.UnsignedPayload
         val isAwsChunked = request.headers.contains("Content-Encoding", "aws-chunked")
diff --git a/runtime/auth/aws-signing-default/api/aws-signing-default.api b/runtime/auth/aws-signing-default/api/aws-signing-default.api
index e00e6d829a..15ca42c07e 100644
--- a/runtime/auth/aws-signing-default/api/aws-signing-default.api
+++ b/runtime/auth/aws-signing-default/api/aws-signing-default.api
@@ -5,7 +5,7 @@ public final class aws/smithy/kotlin/runtime/auth/awssigning/DefaultAwsSignerBui
 	public final fun setTelemetryProvider (Laws/smithy/kotlin/runtime/telemetry/TelemetryProvider;)V
 }
 
-public final class aws/smithy/kotlin/runtime/auth/awssigning/DefaultAwsSignerKt {
+public final class aws/smithy/kotlin/runtime/auth/awssigning/DefaultAwsSignerJVMKt {
 	public static final fun DefaultAwsSigner (Lkotlin/jvm/functions/Function1;)Laws/smithy/kotlin/runtime/auth/awssigning/AwsSigner;
 	public static final fun getDefaultAwsSigner ()Laws/smithy/kotlin/runtime/auth/awssigning/AwsSigner;
 }
diff --git a/runtime/auth/aws-signing-default/build.gradle.kts b/runtime/auth/aws-signing-default/build.gradle.kts
index 22e20d39fd..71781c66c7 100644
--- a/runtime/auth/aws-signing-default/build.gradle.kts
+++ b/runtime/auth/aws-signing-default/build.gradle.kts
@@ -25,5 +25,11 @@ kotlin {
         all {
             languageSettings.optIn("aws.smithy.kotlin.runtime.InternalApi")
         }
+
+        nativeMain {
+            dependencies {
+                implementation(project(":runtime:auth:aws-signing-crt"))
+            }
+        }
     }
 }
diff --git a/runtime/auth/aws-signing-default/common/src/aws/smithy/kotlin/runtime/auth/awssigning/DefaultAwsSigner.kt b/runtime/auth/aws-signing-default/common/src/aws/smithy/kotlin/runtime/auth/awssigning/DefaultAwsSigner.kt
index 85896349b1..df5d2076b9 100644
--- a/runtime/auth/aws-signing-default/common/src/aws/smithy/kotlin/runtime/auth/awssigning/DefaultAwsSigner.kt
+++ b/runtime/auth/aws-signing-default/common/src/aws/smithy/kotlin/runtime/auth/awssigning/DefaultAwsSigner.kt
@@ -4,136 +4,5 @@
  */
 package aws.smithy.kotlin.runtime.auth.awssigning
 
-import aws.smithy.kotlin.runtime.ExperimentalApi
-import aws.smithy.kotlin.runtime.http.Headers
-import aws.smithy.kotlin.runtime.http.request.HttpRequest
-import aws.smithy.kotlin.runtime.telemetry.TelemetryProvider
-import aws.smithy.kotlin.runtime.telemetry.logging.logger
-import aws.smithy.kotlin.runtime.time.TimestampFormat
-import kotlin.coroutines.coroutineContext
-
 /** The default implementation of [AwsSigner] */
-public val DefaultAwsSigner: AwsSigner = DefaultAwsSignerImpl()
-
-/** Creates a customized instance of [AwsSigner] */
-@Suppress("ktlint:standard:function-naming")
-public fun DefaultAwsSigner(block: DefaultAwsSignerBuilder.() -> Unit): AwsSigner =
-    DefaultAwsSignerBuilder().apply(block).build()
-
-/** A builder class for creating instances of [AwsSigner] using the default implementation */
-public class DefaultAwsSignerBuilder {
-    public var telemetryProvider: TelemetryProvider? = null
-
-    public fun build(): AwsSigner = DefaultAwsSignerImpl(
-        telemetryProvider = telemetryProvider,
-    )
-}
-
-private val AwsSigningAlgorithm.signatureCalculator
-    get() = when (this) {
-        AwsSigningAlgorithm.SIGV4 -> SignatureCalculator.SigV4
-        AwsSigningAlgorithm.SIGV4_ASYMMETRIC -> SignatureCalculator.SigV4a
-    }
-
-@OptIn(ExperimentalApi::class)
-internal class DefaultAwsSignerImpl(
-    private val canonicalizer: Canonicalizer = Canonicalizer.Default,
-    private val requestMutator: RequestMutator = RequestMutator.Default,
-    private val telemetryProvider: TelemetryProvider? = null,
-) : AwsSigner {
-    override suspend fun sign(request: HttpRequest, config: AwsSigningConfig): AwsSigningResult<HttpRequest> {
-        val logger = telemetryProvider?.loggerProvider?.getOrCreateLogger("DefaultAwsSigner")
-            ?: coroutineContext.logger<DefaultAwsSignerImpl>()
-
-        val canonical = canonicalizer.canonicalRequest(request, config)
-        if (config.logRequest) {
-            logger.trace { "Canonical request:\n${canonical.requestString}" }
-        }
-
-        val signatureCalculator = config.algorithm.signatureCalculator
-
-        val stringToSign = signatureCalculator.stringToSign(canonical.requestString, config)
-        logger.trace { "String to sign:\n$stringToSign" }
-
-        val signingKey = signatureCalculator.signingKey(config)
-
-        val signature = signatureCalculator.calculate(signingKey, stringToSign)
-        logger.debug { "Calculated signature: $signature" }
-
-        val signedRequest = requestMutator.appendAuth(config, canonical, signature)
-
-        return AwsSigningResult(signedRequest, signature.encodeToByteArray())
-    }
-
-    override suspend fun signChunk(
-        chunkBody: ByteArray,
-        prevSignature: ByteArray,
-        config: AwsSigningConfig,
-    ): AwsSigningResult<Unit> {
-        val logger = telemetryProvider?.loggerProvider?.getOrCreateLogger("DefaultAwsSigner")
-            ?: coroutineContext.logger<DefaultAwsSignerImpl>()
-
-        val signatureCalculator = config.algorithm.signatureCalculator
-
-        val stringToSign = signatureCalculator.chunkStringToSign(chunkBody, prevSignature, config)
-        logger.trace { "Chunk string to sign:\n$stringToSign" }
-
-        val signingKey = signatureCalculator.signingKey(config)
-
-        val signature = signatureCalculator.calculate(signingKey, stringToSign)
-        logger.debug { "Calculated chunk signature: $signature" }
-
-        return AwsSigningResult(Unit, signature.encodeToByteArray())
-    }
-
-    override suspend fun signChunkTrailer(
-        trailingHeaders: Headers,
-        prevSignature: ByteArray,
-        config: AwsSigningConfig,
-    ): AwsSigningResult<Unit> {
-        val logger = telemetryProvider?.loggerProvider?.getOrCreateLogger("DefaultAwsSigner")
-            ?: coroutineContext.logger<DefaultAwsSignerImpl>()
-
-        val signatureCalculator = config.algorithm.signatureCalculator
-
-        // FIXME - can we share canonicalization code more than we are..., also this reduce is inefficient.
-        // canonicalize the headers
-        val trailingHeadersBytes = trailingHeaders.entries().sortedBy { e -> e.key.lowercase() }
-            .map { e ->
-                buildString {
-                    append(e.key.lowercase())
-                    append(":")
-                    append(e.value.joinToString(",") { v -> v.trim() })
-                    append("\n")
-                }.encodeToByteArray()
-            }.reduce { acc, bytes -> acc + bytes }
-
-        val stringToSign = signatureCalculator.chunkTrailerStringToSign(trailingHeadersBytes, prevSignature, config)
-        logger.trace { "Chunk trailer string to sign:\n$stringToSign" }
-
-        val signingKey = signatureCalculator.signingKey(config)
-
-        val signature = signatureCalculator.calculate(signingKey, stringToSign)
-        logger.debug { "Calculated chunk signature: $signature" }
-
-        return AwsSigningResult(Unit, signature.encodeToByteArray())
-    }
-}
-
-/**
- * Formats a credential scope consisting of a signing date, region (SigV4 only), service, and a signature type
- */
-internal val AwsSigningConfig.credentialScope: String
-    get() = run {
-        val signingDate = signingDate.format(TimestampFormat.ISO_8601_CONDENSED_DATE)
-        return when (algorithm) {
-            AwsSigningAlgorithm.SIGV4 -> "$signingDate/$region/$service/aws4_request"
-            AwsSigningAlgorithm.SIGV4_ASYMMETRIC -> "$signingDate/$service/aws4_request"
-        }
-    }
-
-/**
- * Formats the value for a credential header/parameter
- */
-internal fun credentialValue(config: AwsSigningConfig): String =
-    "${config.credentials.accessKeyId}/${config.credentialScope}"
+public expect val DefaultAwsSigner: AwsSigner
diff --git a/runtime/auth/aws-signing-default/common/src/aws/smithy/kotlin/runtime/auth/awssigning/RequestMutator.kt b/runtime/auth/aws-signing-default/common/src/aws/smithy/kotlin/runtime/auth/awssigning/RequestMutator.kt
index 0c1882cd54..ee67e7833b 100644
--- a/runtime/auth/aws-signing-default/common/src/aws/smithy/kotlin/runtime/auth/awssigning/RequestMutator.kt
+++ b/runtime/auth/aws-signing-default/common/src/aws/smithy/kotlin/runtime/auth/awssigning/RequestMutator.kt
@@ -5,6 +5,7 @@
 package aws.smithy.kotlin.runtime.auth.awssigning
 
 import aws.smithy.kotlin.runtime.http.request.HttpRequest
+import aws.smithy.kotlin.runtime.time.TimestampFormat
 
 /**
  * An object that can mutate requests to include signing attributes.
@@ -55,3 +56,21 @@ internal class DefaultRequestMutator : RequestMutator {
         return canonical.request.build()
     }
 }
+
+/**
+ * Formats a credential scope consisting of a signing date, region (SigV4 only), service, and a signature type
+ */
+internal val AwsSigningConfig.credentialScope: String
+    get() {
+        val signingDate = signingDate.format(TimestampFormat.ISO_8601_CONDENSED_DATE)
+        return when (algorithm) {
+            AwsSigningAlgorithm.SIGV4 -> "$signingDate/$region/$service/aws4_request"
+            AwsSigningAlgorithm.SIGV4_ASYMMETRIC -> "$signingDate/$service/aws4_request"
+        }
+    }
+
+/**
+ * Formats the value for a credential header/parameter
+ */
+internal fun credentialValue(config: AwsSigningConfig): String =
+    "${config.credentials.accessKeyId}/${config.credentialScope}"
diff --git a/runtime/auth/aws-signing-default/jvm/src/aws/smithy/kotlin/runtime/auth/awssigning/DefaultAwsSignerJVM.kt b/runtime/auth/aws-signing-default/jvm/src/aws/smithy/kotlin/runtime/auth/awssigning/DefaultAwsSignerJVM.kt
new file mode 100644
index 0000000000..ea1f4723d6
--- /dev/null
+++ b/runtime/auth/aws-signing-default/jvm/src/aws/smithy/kotlin/runtime/auth/awssigning/DefaultAwsSignerJVM.kt
@@ -0,0 +1,120 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package aws.smithy.kotlin.runtime.auth.awssigning
+
+import aws.smithy.kotlin.runtime.ExperimentalApi
+import aws.smithy.kotlin.runtime.http.Headers
+import aws.smithy.kotlin.runtime.http.request.HttpRequest
+import aws.smithy.kotlin.runtime.telemetry.TelemetryProvider
+import aws.smithy.kotlin.runtime.telemetry.logging.logger
+import kotlin.coroutines.coroutineContext
+
+/** The default implementation of [AwsSigner] */
+public actual val DefaultAwsSigner: AwsSigner = DefaultAwsSignerImpl()
+
+/** Creates a customized instance of [AwsSigner] */
+@Suppress("ktlint:standard:function-naming")
+public fun DefaultAwsSigner(block: DefaultAwsSignerBuilder.() -> Unit): AwsSigner =
+    DefaultAwsSignerBuilder().apply(block).build()
+
+/** A builder class for creating instances of [AwsSigner] using the default implementation */
+public class DefaultAwsSignerBuilder {
+    public var telemetryProvider: TelemetryProvider? = null
+
+    public fun build(): AwsSigner = DefaultAwsSignerImpl(
+        telemetryProvider = telemetryProvider,
+    )
+}
+
+private val AwsSigningAlgorithm.signatureCalculator
+    get() = when (this) {
+        AwsSigningAlgorithm.SIGV4 -> SignatureCalculator.SigV4
+        AwsSigningAlgorithm.SIGV4_ASYMMETRIC -> SignatureCalculator.SigV4a
+    }
+
+@OptIn(ExperimentalApi::class)
+internal class DefaultAwsSignerImpl(
+    private val canonicalizer: Canonicalizer = Canonicalizer.Default,
+    private val requestMutator: RequestMutator = RequestMutator.Default,
+    private val telemetryProvider: TelemetryProvider? = null,
+) : AwsSigner {
+    override suspend fun sign(request: HttpRequest, config: AwsSigningConfig): AwsSigningResult<HttpRequest> {
+        val logger = telemetryProvider?.loggerProvider?.getOrCreateLogger("DefaultAwsSigner")
+            ?: coroutineContext.logger<DefaultAwsSignerImpl>()
+
+        val canonical = canonicalizer.canonicalRequest(request, config)
+        if (config.logRequest) {
+            logger.trace { "Canonical request:\n${canonical.requestString}" }
+        }
+
+        val signatureCalculator = config.algorithm.signatureCalculator
+
+        val stringToSign = signatureCalculator.stringToSign(canonical.requestString, config)
+        logger.trace { "String to sign:\n$stringToSign" }
+
+        val signingKey = signatureCalculator.signingKey(config)
+
+        val signature = signatureCalculator.calculate(signingKey, stringToSign)
+        logger.debug { "Calculated signature: $signature" }
+
+        val signedRequest = requestMutator.appendAuth(config, canonical, signature)
+
+        return AwsSigningResult(signedRequest, signature.encodeToByteArray())
+    }
+
+    override suspend fun signChunk(
+        chunkBody: ByteArray,
+        prevSignature: ByteArray,
+        config: AwsSigningConfig,
+    ): AwsSigningResult<Unit> {
+        val logger = telemetryProvider?.loggerProvider?.getOrCreateLogger("DefaultAwsSigner")
+            ?: coroutineContext.logger<DefaultAwsSignerImpl>()
+
+        val signatureCalculator = config.algorithm.signatureCalculator
+
+        val stringToSign = signatureCalculator.chunkStringToSign(chunkBody, prevSignature, config)
+        logger.trace { "Chunk string to sign:\n$stringToSign" }
+
+        val signingKey = signatureCalculator.signingKey(config)
+
+        val signature = signatureCalculator.calculate(signingKey, stringToSign)
+        logger.debug { "Calculated chunk signature: $signature" }
+
+        return AwsSigningResult(Unit, signature.encodeToByteArray())
+    }
+
+    override suspend fun signChunkTrailer(
+        trailingHeaders: Headers,
+        prevSignature: ByteArray,
+        config: AwsSigningConfig,
+    ): AwsSigningResult<Unit> {
+        val logger = telemetryProvider?.loggerProvider?.getOrCreateLogger("DefaultAwsSigner")
+            ?: coroutineContext.logger<DefaultAwsSignerImpl>()
+
+        val signatureCalculator = config.algorithm.signatureCalculator
+
+        // FIXME - can we share canonicalization code more than we are..., also this reduce is inefficient.
+        // canonicalize the headers
+        val trailingHeadersBytes = trailingHeaders.entries().sortedBy { e -> e.key.lowercase() }
+            .map { e ->
+                buildString {
+                    append(e.key.lowercase())
+                    append(":")
+                    append(e.value.joinToString(",") { v -> v.trim() })
+                    append("\n")
+                }.encodeToByteArray()
+            }.reduce { acc, bytes -> acc + bytes }
+
+        val stringToSign = signatureCalculator.chunkTrailerStringToSign(trailingHeadersBytes, prevSignature, config)
+        logger.trace { "Chunk trailer string to sign:\n$stringToSign" }
+
+        val signingKey = signatureCalculator.signingKey(config)
+
+        val signature = signatureCalculator.calculate(signingKey, stringToSign)
+        logger.debug { "Calculated chunk signature: $signature" }
+
+        return AwsSigningResult(Unit, signature.encodeToByteArray())
+    }
+}
diff --git a/runtime/auth/aws-signing-default/native/src/aws/smithy/kotlin/runtime/auth/awssigning/DefaultAwsSignerNative.kt b/runtime/auth/aws-signing-default/native/src/aws/smithy/kotlin/runtime/auth/awssigning/DefaultAwsSignerNative.kt
new file mode 100644
index 0000000000..0b9335ec1d
--- /dev/null
+++ b/runtime/auth/aws-signing-default/native/src/aws/smithy/kotlin/runtime/auth/awssigning/DefaultAwsSignerNative.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.auth.awssigning
+
+import aws.smithy.kotlin.runtime.auth.awssigning.crt.CrtAwsSigner
+
+/** The default implementation of [AwsSigner] */
+public actual val DefaultAwsSigner: AwsSigner = CrtAwsSigner
diff --git a/runtime/auth/aws-signing-tests/common/src/aws/smithy/kotlin/runtime/auth/awssigning/tests/AwsChunkedByteReadChannelTestBase.kt b/runtime/auth/aws-signing-tests/common/src/aws/smithy/kotlin/runtime/auth/awssigning/tests/AwsChunkedByteReadChannelTestBase.kt
index 3374dedc42..f86ef5ba3a 100644
--- a/runtime/auth/aws-signing-tests/common/src/aws/smithy/kotlin/runtime/auth/awssigning/tests/AwsChunkedByteReadChannelTestBase.kt
+++ b/runtime/auth/aws-signing-tests/common/src/aws/smithy/kotlin/runtime/auth/awssigning/tests/AwsChunkedByteReadChannelTestBase.kt
@@ -5,7 +5,6 @@
 
 package aws.smithy.kotlin.runtime.auth.awssigning.tests
 
-import aws.smithy.kotlin.runtime.IgnoreNative
 import aws.smithy.kotlin.runtime.auth.awssigning.*
 import aws.smithy.kotlin.runtime.auth.awssigning.internal.CHUNK_SIZE_BYTES
 import aws.smithy.kotlin.runtime.io.*
@@ -18,7 +17,6 @@ import kotlin.test.*
 import kotlin.time.Duration.Companion.milliseconds
 
 abstract class AwsChunkedByteReadChannelTestBase : AwsChunkedTestBase(AwsChunkedReaderFactory.Channel) {
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native Implementation
     @Test
     fun testSlowProducerMultipleChunksPartialLast(): TestResult = runTest {
         val numChunks = 6
diff --git a/runtime/auth/aws-signing-tests/common/src/aws/smithy/kotlin/runtime/auth/awssigning/tests/AwsChunkedTestBase.kt b/runtime/auth/aws-signing-tests/common/src/aws/smithy/kotlin/runtime/auth/awssigning/tests/AwsChunkedTestBase.kt
index be05b88eb9..10247109ae 100644
--- a/runtime/auth/aws-signing-tests/common/src/aws/smithy/kotlin/runtime/auth/awssigning/tests/AwsChunkedTestBase.kt
+++ b/runtime/auth/aws-signing-tests/common/src/aws/smithy/kotlin/runtime/auth/awssigning/tests/AwsChunkedTestBase.kt
@@ -5,7 +5,6 @@
 
 package aws.smithy.kotlin.runtime.auth.awssigning.tests
 
-import aws.smithy.kotlin.runtime.IgnoreNative
 import aws.smithy.kotlin.runtime.auth.awssigning.*
 import aws.smithy.kotlin.runtime.auth.awssigning.internal.CHUNK_SIZE_BYTES
 import aws.smithy.kotlin.runtime.http.DeferredHeaders
@@ -172,7 +171,6 @@ abstract class AwsChunkedTestBase(
         return length
     }
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native Implementation
     @Test
     fun testReadNegativeOffset(): TestResult = runTest {
         val dataLengthBytes = CHUNK_SIZE_BYTES
@@ -186,7 +184,6 @@ abstract class AwsChunkedTestBase(
         }
     }
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native Implementation
     @Test
     fun testReadExactBytes(): TestResult = runTest {
         val dataLengthBytes = CHUNK_SIZE_BYTES
@@ -220,7 +217,6 @@ abstract class AwsChunkedTestBase(
         assertTrue(awsChunked.isClosedForRead())
     }
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native Implementation
     @Test
     fun testReadExcessiveBytes(): TestResult = runTest {
         val dataLengthBytes = CHUNK_SIZE_BYTES
@@ -250,7 +246,6 @@ abstract class AwsChunkedTestBase(
         assertTrue(awsChunked.isClosedForRead())
     }
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native Implementation
     @Test
     fun testReadFewerBytes(): TestResult = runTest {
         val dataLengthBytes = CHUNK_SIZE_BYTES
@@ -277,7 +272,6 @@ abstract class AwsChunkedTestBase(
         assertFalse(awsChunked.isClosedForRead())
     }
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native Implementation
     @Test
     fun testReadMultipleFullChunks(): TestResult = runTest {
         val numChunks = 5
@@ -325,7 +319,6 @@ abstract class AwsChunkedTestBase(
         assertTrue(awsChunked.isClosedForRead())
     }
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native Implementation
     @Test
     fun testReadMultipleChunksLastChunkNotFull(): TestResult = runTest {
         val numChunks = 6
@@ -391,7 +384,6 @@ abstract class AwsChunkedTestBase(
         assertEquals(0, chunkSizes.last())
     }
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native implementation
     @Test
     fun testReadWithTrailingHeaders(): TestResult = runTest {
         val dataLengthBytes = CHUNK_SIZE_BYTES
@@ -442,7 +434,6 @@ abstract class AwsChunkedTestBase(
         assertEquals(expectedTrailerSignature.decodeToString(), trailerSignature)
     }
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native implementation
     @Test
     fun testUnsignedChunk(): TestResult = runTest {
         val dataLengthBytes = CHUNK_SIZE_BYTES
@@ -474,7 +465,6 @@ abstract class AwsChunkedTestBase(
         assertEquals(chunkSizes[1], 0)
     }
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native implementation
     @Test
     fun testUnsignedChunkWithTrailingHeaders(): TestResult = runTest {
         val dataLengthBytes = CHUNK_SIZE_BYTES
diff --git a/runtime/auth/aws-signing-tests/common/src/aws/smithy/kotlin/runtime/auth/awssigning/tests/BasicSigningTestBase.kt b/runtime/auth/aws-signing-tests/common/src/aws/smithy/kotlin/runtime/auth/awssigning/tests/BasicSigningTestBase.kt
index 3f4e1e1d17..2a517fc090 100644
--- a/runtime/auth/aws-signing-tests/common/src/aws/smithy/kotlin/runtime/auth/awssigning/tests/BasicSigningTestBase.kt
+++ b/runtime/auth/aws-signing-tests/common/src/aws/smithy/kotlin/runtime/auth/awssigning/tests/BasicSigningTestBase.kt
@@ -4,7 +4,6 @@
  */
 package aws.smithy.kotlin.runtime.auth.awssigning.tests
 
-import aws.smithy.kotlin.runtime.IgnoreNative
 import aws.smithy.kotlin.runtime.auth.awscredentials.Credentials
 import aws.smithy.kotlin.runtime.auth.awssigning.*
 import aws.smithy.kotlin.runtime.http.HttpBody
@@ -56,7 +55,6 @@ public abstract class BasicSigningTestBase : HasSigner {
         credentials = DEFAULT_TEST_CREDENTIALS
     }
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native Implementation
     @Test
     public fun testSignRequestSigV4(): TestResult = runTest {
         // sanity test
@@ -85,7 +83,6 @@ public abstract class BasicSigningTestBase : HasSigner {
         assertEquals(expectedSig, result.signature.decodeToString())
     }
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native Implementation
     @Test
     public open fun testSignRequestSigV4Asymmetric(): TestResult = runTest {
         // sanity test
@@ -168,7 +165,6 @@ public abstract class BasicSigningTestBase : HasSigner {
         return chunk
     }
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native Implementation
     @Test
     public fun testSignChunks(): TestResult = runTest {
         val request = createChunkedTestRequest()
@@ -192,7 +188,6 @@ public abstract class BasicSigningTestBase : HasSigner {
         assertEquals(EXPECTED_FINAL_CHUNK_SIGNATURE, finalChunkResult.signature.decodeToString())
     }
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native Implementation
     @Test
     public fun testSigningCopiesInput(): TestResult = runTest {
         // sanity test the signer doesn't mutate the input and instead copies to a new request
diff --git a/runtime/auth/http-auth-aws/common/test/aws/smithy/kotlin/runtime/http/auth/AwsHttpSignerTestBase.kt b/runtime/auth/http-auth-aws/common/test/aws/smithy/kotlin/runtime/http/auth/AwsHttpSignerTestBase.kt
index 1786744b01..6797ed74fb 100644
--- a/runtime/auth/http-auth-aws/common/test/aws/smithy/kotlin/runtime/http/auth/AwsHttpSignerTestBase.kt
+++ b/runtime/auth/http-auth-aws/common/test/aws/smithy/kotlin/runtime/http/auth/AwsHttpSignerTestBase.kt
@@ -134,7 +134,6 @@ public abstract class AwsHttpSignerTestBase(
         assertEquals(expectedSig, signed.headers["Authorization"])
     }
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native Implementation.
     @Test
     public fun testSignReplayableStreamingRequest(): TestResult = runTest {
         val op = buildOperation(streaming = true)
@@ -148,7 +147,7 @@ public abstract class AwsHttpSignerTestBase(
         assertEquals(expectedSig, signed.headers["Authorization"])
     }
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native Implementation.
+    @IgnoreNative // FIXME Our JVM implementation does not sign `transfer-encoding`, but CRT does, causing a signature mismatch. Upgrade to latest version of aws-c-auth to get the fix.
     @Test
     public fun testSignAwsChunkedStreamNonReplayable(): TestResult = runTest {
         val op = buildOperation(streaming = true, replayable = false, requestBody = "a".repeat(AWS_CHUNKED_THRESHOLD + 1))
@@ -162,7 +161,7 @@ public abstract class AwsHttpSignerTestBase(
         assertEquals(expectedSig, signed.headers["Authorization"])
     }
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native Implementation.
+    @IgnoreNative // FIXME Our JVM implementation does not sign `transfer-encoding`, but CRT does, causing a signature mismatch. Upgrade to latest version of aws-c-auth to get the fix.
     @Test
     public fun testSignAwsChunkedStreamReplayable(): TestResult = runTest {
         val op = buildOperation(streaming = true, replayable = true, requestBody = "a".repeat(AWS_CHUNKED_THRESHOLD + 1))
@@ -176,7 +175,7 @@ public abstract class AwsHttpSignerTestBase(
         assertEquals(expectedSig, signed.headers["Authorization"])
     }
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native Implementation.
+    @IgnoreNative // FIXME Our JVM implementation does not sign `transfer-encoding`, but CRT does, causing a signature mismatch. Upgrade to latest version of aws-c-auth to get the fix.
     @Test
     public fun testSignOneShotStream(): TestResult = runTest {
         val op = buildOperation(streaming = true, replayable = false)
diff --git a/runtime/crt-util/jvmAndNative/test/aws/smithy/kotlin/runtime/crt/ReadChannelBodyStreamTest.kt b/runtime/crt-util/jvmAndNative/test/aws/smithy/kotlin/runtime/crt/ReadChannelBodyStreamTest.kt
index b4afa25c91..eb0acf777e 100644
--- a/runtime/crt-util/jvmAndNative/test/aws/smithy/kotlin/runtime/crt/ReadChannelBodyStreamTest.kt
+++ b/runtime/crt-util/jvmAndNative/test/aws/smithy/kotlin/runtime/crt/ReadChannelBodyStreamTest.kt
@@ -6,7 +6,6 @@
 package aws.smithy.kotlin.runtime.crt
 
 import aws.sdk.kotlin.crt.io.MutableBuffer
-import aws.smithy.kotlin.runtime.IgnoreNative
 import aws.smithy.kotlin.runtime.io.SdkBuffer
 import aws.smithy.kotlin.runtime.io.SdkByteChannel
 import aws.smithy.kotlin.runtime.io.SdkByteReadChannel
@@ -27,7 +26,6 @@ class ReadChannelBodyStreamTest {
         return MutableBuffer.of(dest) to dest
     }
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native implementation. kotlin.native.internal.FileFailedToInitializeException at null:-1
     @Test
     fun testClose() = runTest {
         val chan = SdkByteChannel()
@@ -44,7 +42,6 @@ class ReadChannelBodyStreamTest {
         assertTrue(stream.sendRequestBody(sendBuffer))
     }
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native implementation. kotlin.native.internal.FileFailedToInitializeException at null:-1
     @Test
     fun testCancellation() = runTest {
         val chan = SdkByteChannel()
@@ -59,7 +56,6 @@ class ReadChannelBodyStreamTest {
         }
     }
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native implementation. kotlin.NotImplementedError at null:-1
     @Test
     fun testReadFully() = runTest {
         val data = byteArrayOf(1, 2, 3, 4, 5)
@@ -75,7 +71,6 @@ class ReadChannelBodyStreamTest {
         }
     }
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native implementation. kotlin.NotImplementedError at null:-1
     @Test
     fun testPartialRead() = runTest {
         val chan = SdkByteReadChannel("123456".encodeToByteArray())
@@ -94,7 +89,6 @@ class ReadChannelBodyStreamTest {
         assertEquals("456", sent2.decodeToString())
     }
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native implementation. kotlin.native.internal.FileFailedToInitializeException at null:-1
     @Test
     fun testLargeTransfer() = runTest {
         val chan = SdkByteChannel()
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
index 09eb88dfd8..e27805bbf6 100644
--- 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
@@ -7,4 +7,8 @@ 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")
+internal actual fun transferRequestBody(outgoing: SdkBuffer, dest: MutableBuffer): Int {
+    val length = minOf(outgoing.size, dest.writeRemaining.toLong())
+    if (length <= 0) return 0
+    return dest.write(outgoing.readByteArray(length))
+}
diff --git a/runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/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
index 7d0b0def83..e509808ec1 100644
--- a/runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/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
@@ -37,7 +37,7 @@ class AsyncStressTest : TestWithLocalServer() {
         }
     }.start()
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native implementation
+    @IgnoreNative // FIXME TlsContext needs to initialize CRT. Segmentation fault.
     @Test
     fun testStreamNotConsumed() = runBlocking {
         // test that filling the stream window and not consuming the body stream still cleans up resources
diff --git a/runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/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
index 7382adcca4..6c09f0dd02 100644
--- a/runtime/protocol/http-client-engines/http-client-engine-crt/jvmAndNative/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
@@ -5,9 +5,9 @@
 
 package aws.smithy.kotlin.runtime.http.engine.crt
 
+import aws.sdk.kotlin.crt.CRT
 import aws.sdk.kotlin.crt.http.*
 import aws.sdk.kotlin.crt.io.byteArrayBuffer
-import aws.smithy.kotlin.runtime.IgnoreNative
 import aws.smithy.kotlin.runtime.http.HttpBody
 import aws.smithy.kotlin.runtime.http.HttpErrorCode
 import aws.smithy.kotlin.runtime.http.HttpException
@@ -153,9 +153,9 @@ class SdkStreamResponseHandlerTest {
         assertEquals(data, respChan.readToBuffer().readUtf8())
     }
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native Implementation.
     @Test
     fun testStreamError() = runTest {
+        CRT.initRuntime() // CRT needs to be initialized for human-readable error codes
         val handler = SdkStreamResponseHandler(mockConn, coroutineContext)
         val stream = MockHttpStream(200)
         val data = "foo bar"
diff --git a/runtime/protocol/http-client/common/test/aws/smithy/kotlin/runtime/http/operation/HttpInterceptorTest.kt b/runtime/protocol/http-client/common/test/aws/smithy/kotlin/runtime/http/operation/HttpInterceptorTest.kt
index ffa4a4d894..5d36840bcf 100644
--- a/runtime/protocol/http-client/common/test/aws/smithy/kotlin/runtime/http/operation/HttpInterceptorTest.kt
+++ b/runtime/protocol/http-client/common/test/aws/smithy/kotlin/runtime/http/operation/HttpInterceptorTest.kt
@@ -5,7 +5,6 @@
 
 package aws.smithy.kotlin.runtime.http.operation
 
-import aws.smithy.kotlin.runtime.IgnoreNative
 import aws.smithy.kotlin.runtime.client.*
 import aws.smithy.kotlin.runtime.http.Headers
 import aws.smithy.kotlin.runtime.http.interceptors.HttpInterceptor
@@ -236,7 +235,6 @@ class HttpInterceptorTest {
         testMapFailure(interceptor)
     }
 
-    @IgnoreNative // FIXME Re-enable after Kotlin/Native Implementation
     @Test
     fun testReadAfterExecutionSuppressedException() = runTest {
         val interceptor = object : HttpInterceptor {
@@ -261,7 +259,9 @@ class HttpInterceptorTest {
             op.roundTrip(client, Unit)
         }
 
-        val cause = assertNotNull(ex.cause)
+        // FIXME Investigate why the exception `ex` and its cause are duplicated on JVM.
+        // On JVM, `ex.cause` has the suppressed exceptions. On Native, `ex` has the suppressed exceptions and it has no cause.
+        val cause = assertNotNull(ex.cause ?: ex)
         assertEquals(1, cause.suppressedExceptions.size)
         assertIs<TestException>(cause.suppressedExceptions.last())
     }
diff --git a/runtime/runtime-core/native/src/aws/smithy/kotlin/runtime/hashing/EcdsaNative.kt b/runtime/runtime-core/native/src/aws/smithy/kotlin/runtime/hashing/EcdsaNative.kt
index a2bca1c4e6..112b60df14 100644
--- a/runtime/runtime-core/native/src/aws/smithy/kotlin/runtime/hashing/EcdsaNative.kt
+++ b/runtime/runtime-core/native/src/aws/smithy/kotlin/runtime/hashing/EcdsaNative.kt
@@ -4,10 +4,7 @@
  */
 package aws.smithy.kotlin.runtime.hashing
 
-// FIXME Implement using aws-c-cal: https://github.com/awslabs/aws-c-cal/blob/main/include/aws/cal/ecc.h
-// Will need to be implemented and exposed in aws-crt-kotlin. Or maybe we can _only_ offer the CRT signer on Native?
-// Will require updating DefaultAwsSigner to be expect/actual and set to CrtSigner on Native.
 /**
  * ECDSA on the SECP256R1 curve.
  */
-public actual fun ecdsaSecp256r1(key: ByteArray, message: ByteArray): ByteArray = TODO("Not yet implemented")
+public actual fun ecdsaSecp256r1(key: ByteArray, message: ByteArray): ByteArray = error("This function should not be invoked on Native, which uses the CrtAwsSigner.")