diff --git a/custom-runtime/src/main/java/com/networknt/aws/lambda/LambdaRuntimeMappers.java b/custom-runtime/src/main/java/com/networknt/aws/lambda/LambdaRuntimeMappers.java
new file mode 100644
index 0000000..0cc8e8b
--- /dev/null
+++ b/custom-runtime/src/main/java/com/networknt/aws/lambda/LambdaRuntimeMappers.java
@@ -0,0 +1,22 @@
+package com.networknt.aws.lambda;
+
+import com.networknt.jackson.JacksonDefaults;
+import tools.jackson.databind.DeserializationFeature;
+import tools.jackson.databind.ObjectMapper;
+
+/**
+ * Shared immutable mapper exclusively for AWS Lambda event payloads in the JVM and native runtimes.
+ * Intentionally accepts unknown event properties, making it more permissive than the framework mapper.
+ * Do not use it for configuration binding or validation.
+ */
+public final class LambdaRuntimeMappers {
+    private static final ObjectMapper MAPPER = JacksonDefaults.builder()
+            .disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES).build();
+
+    private LambdaRuntimeMappers() { }
+
+    /** Returns the event-only mapper, accepting future AWS event properties. */
+    public static ObjectMapper mapper() {
+        return MAPPER;
+    }
+}
diff --git a/custom-runtime/src/main/java/com/networknt/aws/lambda/Runtime.java b/custom-runtime/src/main/java/com/networknt/aws/lambda/Runtime.java
index 0b99f2d..3d7713b 100644
--- a/custom-runtime/src/main/java/com/networknt/aws/lambda/Runtime.java
+++ b/custom-runtime/src/main/java/com/networknt/aws/lambda/Runtime.java
@@ -3,7 +3,6 @@
 import com.amazonaws.services.lambda.runtime.RequestHandler;
 import com.amazonaws.services.lambda.runtime.events.APIGatewayProxyRequestEvent;
 import com.amazonaws.services.lambda.runtime.events.APIGatewayProxyResponseEvent;
-import com.networknt.jackson.JacksonDefaults;
 import com.networknt.utility.NioUtils;
 import java.io.IOException;
 import java.lang.reflect.Method;
@@ -11,14 +10,12 @@
 import java.lang.reflect.ParameterizedType;
 import java.lang.reflect.Type;
 import java.net.HttpURLConnection;
-import tools.jackson.databind.DeserializationFeature;
 import tools.jackson.databind.ObjectMapper;
 
 public class Runtime {
     private static final String REQUEST_ID_HEADER = "lambda-runtime-aws-request-id";
 
-    private static final ObjectMapper OBJECT_MAPPER = JacksonDefaults.builder()
-            .disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES).build();
+    private static final ObjectMapper OBJECT_MAPPER = LambdaRuntimeMappers.mapper();
 
     public static void main(String[] args) throws IOException {
         while(true) {
diff --git a/custom-runtime/src/test/java/com/networknt/aws/lambda/Jackson3RuntimeCompatibilityTest.java b/custom-runtime/src/test/java/com/networknt/aws/lambda/Jackson3RuntimeCompatibilityTest.java
index 387d202..1c60aa0 100644
--- a/custom-runtime/src/test/java/com/networknt/aws/lambda/Jackson3RuntimeCompatibilityTest.java
+++ b/custom-runtime/src/test/java/com/networknt/aws/lambda/Jackson3RuntimeCompatibilityTest.java
@@ -2,8 +2,9 @@
 
 import com.amazonaws.services.lambda.runtime.events.APIGatewayProxyRequestEvent;
 import com.amazonaws.services.lambda.runtime.events.APIGatewayProxyResponseEvent;
+import com.networknt.jackson.JacksonDefaults;
 import org.junit.jupiter.api.Test;
-import tools.jackson.databind.ObjectMapper;
+import tools.jackson.databind.DeserializationFeature;
 
 import java.util.List;
 import java.util.Map;
@@ -14,15 +15,17 @@
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 class Jackson3RuntimeCompatibilityTest {
-    private ObjectMapper runtimeMapper() throws Exception {
-        var field = Runtime.class.getDeclaredField("OBJECT_MAPPER");
-        field.setAccessible(true);
-        return (ObjectMapper) field.get(null);
+    @Test
+    void runtimeAndFrameworkMappersHaveSeparateUnknownPropertyPolicies() {
+        var runtimeMapper = LambdaRuntimeMappers.mapper();
+        var frameworkMapper = JacksonDefaults.builder().build();
+        assertFalse(runtimeMapper.isEnabled(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES));
+        assertTrue(frameworkMapper.isEnabled(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES));
     }
 
     @Test
     void bindsAwsGatewayEventsWithoutJackson2Types() throws Exception {
-        var mapper = runtimeMapper();
+        var mapper = LambdaRuntimeMappers.mapper();
         var request = mapper.readValue("{\"path\":\"/pets\",\"httpMethod\":\"POST\","
                 + "\"body\":\"雪\",\"isBase64Encoded\":true,\"requestContext\":{\"requestId\":\"fixture\"},"
                 + "\"multiValueHeaders\":{\"X-Test\":[\"one\",\"two\"]}}", APIGatewayProxyRequestEvent.class);
@@ -40,12 +43,12 @@ void preservesTheMeasuredResponseWireShape() throws Exception {
                 .withMultiValueHeaders(Map.of("Set-Cookie", List.of("a=1", "b=2")));
         assertEquals("{\"statusCode\":201,\"headers\":{\"Content-Type\":\"application/json\"},"
                 + "\"multiValueHeaders\":{\"Set-Cookie\":[\"a=1\",\"b=2\"]},\"body\":\"雪\\nbody\","
-                + "\"isBase64Encoded\":true}", runtimeMapper().writeValueAsString(response));
+                + "\"isBase64Encoded\":true}", LambdaRuntimeMappers.mapper().writeValueAsString(response));
     }
 
     @Test
     void retainsBuilderBindingAndNullPrimitiveHandling() throws Exception {
-        var mapper = runtimeMapper();
+        var mapper = LambdaRuntimeMappers.mapper();
         var response = mapper.readValue("{\"code\":null,\"message\":\"fixture error\"}", DefaultResponse.class);
         assertEquals(0, response.getCode());
         assertEquals("{\"code\":0,\"message\":\"fixture error\"}", mapper.writeValueAsString(response));
@@ -56,7 +59,7 @@ void retainsBuilderBindingAndNullPrimitiveHandling() throws Exception {
 
     @Test
     void retainsPermissiveRuntimeBinding() throws Exception {
-        var mapper = runtimeMapper();
+        var mapper = LambdaRuntimeMappers.mapper();
         var request = mapper.readValue("{\"futureField\":1,\"isBase64Encoded\":false} {}", APIGatewayProxyRequestEvent.class);
         assertNull(request.getPath());
         assertFalse(request.getIsBase64Encoded());