diff --git a/build.gradle b/build.gradle
index 1c055651..031b6733 100644
--- a/build.gradle
+++ b/build.gradle
@@ -47,8 +47,8 @@ dependencies {
     implementation 'com.google.api.grpc:proto-google-common-protos:2.14.3'
     implementation 'com.squareup.okhttp3:okhttp:4.12.0'
     implementation 'com.squareup.okhttp3:logging-interceptor:4.12.0'
-    implementation 'com.fasterxml.jackson.core:jackson-databind:2.14.2'
-    implementation 'com.fasterxml.jackson.core:jackson-core:2.14.2'
+    implementation 'com.fasterxml.jackson.core:jackson-databind:2.21.4'
+    implementation 'com.fasterxml.jackson.core:jackson-core:2.21.4'
     implementation 'com.google.code.gson:gson:2.9.1'
     implementation 'io.gsonfire:gson-fire:1.8.5'
     implementation 'org.openapitools:jackson-databind-nullable:0.2.6'
@@ -60,7 +60,7 @@ dependencies {
     testImplementation "org.hamcrest:hamcrest:2.2"
     testImplementation 'org.mockito:mockito-inline:4.8.0'
     testImplementation 'org.slf4j:slf4j-simple:2.0.5'
-    testImplementation 'com.fasterxml.jackson.core:jackson-databind:2.14.2'
+    testImplementation 'com.fasterxml.jackson.core:jackson-databind:2.21.4'
     testImplementation 'org.junit.jupiter:junit-jupiter-api:5.8.0'
     testImplementation 'org.junit.platform:junit-platform-launcher:1.8.0'
     testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.8.0'
@@ -155,6 +155,12 @@ task integrationTest(type: Test) {
 import com.github.jengelman.gradle.plugins.shadow.transformers.ServiceFileTransformer
 
 shadowJar {
+    // jackson-core (2.15+) is a multi-release JAR that bundles Java 21 (class-file major 65)
+    // variants under META-INF/versions/21. The Shadow 8.1.1 plugin relocates com.fasterxml
+    // and its ASM cannot read major version 65, so it fails with
+    // "Unsupported class file major version 65". These are JDK-21-only optimizations; dropping
+    // them is safe because the base (Java 8) classes remain and multi-release fallback applies.
+    exclude 'META-INF/versions/21/**'
     relocate 'io.grpc', 'io.pinecone.shadow.io.grpc'
     relocate 'com.google', 'io.pinecone.shadow.com.google'
     relocate 'org.slf4j', 'io.pinecone.shadow.org.slf4j'