diff --git a/.github/workflows/sdk.yml b/.github/workflows/sdk.yml
index b760b26..cd338fc 100644
--- a/.github/workflows/sdk.yml
+++ b/.github/workflows/sdk.yml
@@ -19,13 +19,24 @@ jobs:
       EV_RELAY_HOST: strict.relay.evervault.com
     steps:
       - uses: actions/checkout@v7
-      - name: Set up JDK ${{ matrix.java-version }} with ${{ matrix.distribution }}
+      - name: Set up JDK ${{ matrix.java-version }} test toolchain
         uses: actions/setup-java@v5
         with:
           distribution: 'corretto'
           java-version: ${{ matrix.java-version }}
+      # Gradle 9 requires JVM 17+ to run the Gradle process itself, even
+      # though it can still compile/test against older JDKs via toolchains.
+      # This second setup-java call overwrites JAVA_HOME with a JDK new
+      # enough to launch Gradle, while leaving JAVA_HOME_<version>_X64 from
+      # the step above in place so Gradle's toolchain auto-detection can
+      # still find the matrix JDK to actually run the tests on.
+      - name: Set up JDK 21 to run Gradle
+        uses: actions/setup-java@v5
+        with:
+          distribution: 'corretto'
+          java-version: '21'
       - name: unit tests
-        run: ./gradlew clean test --info
+        run: ./gradlew clean test --info -PtestJavaVersion=${{ matrix.java-version }}
         env:
           TEST_EV_APP_ID: ${{ secrets.TEST_EV_APP_ID }}
           TEST_EV_API_KEY: ${{ secrets.TEST_EV_API_KEY }}
diff --git a/build.gradle b/build.gradle
index 06d09c4..fd4b6df 100644
--- a/build.gradle
+++ b/build.gradle
@@ -5,7 +5,7 @@ buildscript {
 }
 
 plugins {
-    id 'io.github.gradle-nexus.publish-plugin' version '1.1.0'
+    id 'io.github.gradle-nexus.publish-plugin' version '2.0.0'
 }
 
 group 'com.evervault'
diff --git a/buildscript-gradle.lockfile b/buildscript-gradle.lockfile
index 7d97a8e..6f2495f 100644
--- a/buildscript-gradle.lockfile
+++ b/buildscript-gradle.lockfile
@@ -1,6 +1,6 @@
 # This is a Gradle generated file for dependency locking.
 # Manual edits can break the build and are not advised.
 # This file is expected to be part of source control.
-io.github.gradle-nexus.publish-plugin:io.github.gradle-nexus.publish-plugin.gradle.plugin:1.1.0=classpath
-io.github.gradle-nexus:publish-plugin:1.1.0=classpath
+io.github.gradle-nexus.publish-plugin:io.github.gradle-nexus.publish-plugin.gradle.plugin:2.0.0=classpath
+io.github.gradle-nexus:publish-plugin:2.0.0=classpath
 empty=
diff --git a/gradle.properties b/gradle.properties
new file mode 100644
index 0000000..cdd130d
--- /dev/null
+++ b/gradle.properties
@@ -0,0 +1 @@
+org.gradle.java.installations.fromEnv=JAVA_HOME_8_X64,JAVA_HOME_11_X64,JAVA_HOME_16_X64,JAVA_HOME_17_X64,JAVA_HOME_21_X64
diff --git a/gradle/wrapper/gradle-wrapper.jar b/gradle/wrapper/gradle-wrapper.jar
index 7454180..b1b8ef5 100644
Binary files a/gradle/wrapper/gradle-wrapper.jar and b/gradle/wrapper/gradle-wrapper.jar differ
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index d951fac..aaf5cca 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.7-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-9.6.1-all.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
diff --git a/gradlew b/gradlew
index 1b6c787..249efbb 100755
--- a/gradlew
+++ b/gradlew
@@ -1,7 +1,7 @@
 #!/bin/sh
 
 #
-# Copyright © 2015-2021 the original authors.
+# Copyright © 2015 the original authors.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -15,10 +15,12 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 #
+# SPDX-License-Identifier: Apache-2.0
+#
 
 ##############################################################################
 #
-#   Gradle start up script for POSIX generated by Gradle.
+#   gradlew start up script for POSIX generated by Gradle.
 #
 #   Important for running:
 #
@@ -27,7 +29,7 @@
 #       bash, then to run this script, type that shell name before the whole
 #       command line, like:
 #
-#           ksh Gradle
+#           ksh gradlew
 #
 #       Busybox and similar reduced shells will NOT work, because this script
 #       requires all of these POSIX shell features:
@@ -55,7 +57,7 @@
 #       Darwin, MinGW, and NonStop.
 #
 #   (3) This script is generated from the Groovy template
-#       https://github.com/gradle/gradle/blob/master/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       https://github.com/gradle/gradle/blob/3d91ce3b8caaf77ad09f381f43615b715b53f72c/platforms/jvm/plugins-application/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
 #       within the Gradle project.
 #
 #       You can find Gradle at https://github.com/gradle/gradle/.
@@ -80,13 +82,11 @@ do
     esac
 done
 
-APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
-
-APP_NAME="Gradle"
+# This is normally unused
+# shellcheck disable=SC2034
 APP_BASE_NAME=${0##*/}
-
-# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
-DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+# Discard cd standard output in case $CDPATH is set (https://github.com/gradle/gradle/issues/25036)
+APP_HOME=$( cd -P "${APP_HOME:-./}" > /dev/null && printf '%s\n' "$PWD" ) || exit
 
 # Use the maximum available, or set MAX_FD != -1 to use that value.
 MAX_FD=maximum
@@ -114,7 +114,6 @@ case "$( uname )" in                #(
   NONSTOP* )        nonstop=true ;;
 esac
 
-CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
 
 
 # Determine the Java command to use to start the JVM.
@@ -133,22 +132,29 @@ location of your Java installation."
     fi
 else
     JAVACMD=java
-    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+    if ! command -v java >/dev/null 2>&1
+    then
+        die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
 
 Please set the JAVA_HOME variable in your environment to match the
 location of your Java installation."
+    fi
 fi
 
 # Increase the maximum file descriptors if we can.
 if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
     case $MAX_FD in #(
       max*)
+        # In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
         MAX_FD=$( ulimit -H -n ) ||
             warn "Could not query maximum file descriptor limit"
     esac
     case $MAX_FD in  #(
       '' | soft) :;; #(
       *)
+        # In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
         ulimit -n "$MAX_FD" ||
             warn "Could not set maximum file descriptor limit to $MAX_FD"
     esac
@@ -165,7 +171,6 @@ fi
 # For Cygwin or MSYS, switch paths to Windows format before running java
 if "$cygwin" || "$msys" ; then
     APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
-    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
 
     JAVACMD=$( cygpath --unix "$JAVACMD" )
 
@@ -193,18 +198,27 @@ if "$cygwin" || "$msys" ; then
     done
 fi
 
-# Collect all arguments for the java command;
-#   * $DEFAULT_JVM_OPTS, $JAVA_OPTS, and $GRADLE_OPTS can contain fragments of
-#     shell script including quotes and variable substitutions, so put them in
-#     double quotes to make sure that they get re-expanded; and
-#   * put everything else in single quotes, so that it's not re-expanded.
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Collect all arguments for the java command:
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and optsEnvironmentVar are not allowed to contain shell fragments,
+#     and any embedded shellness will be escaped.
+#   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
+#     treated as '${Hostname}' itself on the command line.
 
 set -- \
         "-Dorg.gradle.appname=$APP_BASE_NAME" \
-        -classpath "$CLASSPATH" \
-        org.gradle.wrapper.GradleWrapperMain \
+        -jar "$APP_HOME/gradle/wrapper/gradle-wrapper.jar" \
         "$@"
 
+# Stop when "xargs" is not available.
+if ! command -v xargs >/dev/null 2>&1
+then
+    die "xargs is not available"
+fi
+
 # Use "xargs" to parse quoted args.
 #
 # With -n1 it outputs one arg per line, with the quotes and backslashes removed.
diff --git a/gradlew.bat b/gradlew.bat
index 107acd3..a51ec4f 100644
--- a/gradlew.bat
+++ b/gradlew.bat
@@ -13,19 +13,22 @@
 @rem See the License for the specific language governing permissions and
 @rem limitations under the License.
 @rem
+@rem SPDX-License-Identifier: Apache-2.0
+@rem
 
-@if "%DEBUG%" == "" @echo off
+@if "%DEBUG%"=="" @echo off
 @rem ##########################################################################
 @rem
-@rem  Gradle startup script for Windows
+@rem  gradlew startup script for Windows
 @rem
 @rem ##########################################################################
 
-@rem Set local scope for the variables with windows NT shell
-if "%OS%"=="Windows_NT" setlocal
+@rem Set local scope for the variables, and ensure extensions are enabled
+setlocal EnableExtensions
 
 set DIRNAME=%~dp0
-if "%DIRNAME%" == "" set DIRNAME=.
+if "%DIRNAME%"=="" set DIRNAME=.
+@rem This is normally unused
 set APP_BASE_NAME=%~n0
 set APP_HOME=%DIRNAME%
 
@@ -40,15 +43,15 @@ if defined JAVA_HOME goto findJavaFromJavaHome
 
 set JAVA_EXE=java.exe
 %JAVA_EXE% -version >NUL 2>&1
-if "%ERRORLEVEL%" == "0" goto execute
+if %ERRORLEVEL% equ 0 goto execute
 
-echo.
-echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
-echo.
-echo Please set the JAVA_HOME variable in your environment to match the
-echo location of your Java installation.
+echo. 1>&2
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH. 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
 
-goto fail
+"%COMSPEC%" /c exit 1
 
 :findJavaFromJavaHome
 set JAVA_HOME=%JAVA_HOME:"=%
@@ -56,34 +59,24 @@ set JAVA_EXE=%JAVA_HOME%/bin/java.exe
 
 if exist "%JAVA_EXE%" goto execute
 
-echo.
-echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
-echo.
-echo Please set the JAVA_HOME variable in your environment to match the
-echo location of your Java installation.
+echo. 1>&2
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME% 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
 
-goto fail
+"%COMSPEC%" /c exit 1
 
 :execute
 @rem Setup the command line
 
-set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
-
-
-@rem Execute Gradle
-"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
-
-:end
-@rem End local scope for the variables with windows NT shell
-if "%ERRORLEVEL%"=="0" goto mainEnd
 
-:fail
-rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
-rem the _cmd.exe /c_ return code!
-if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
-exit /b 1
 
-:mainEnd
-if "%OS%"=="Windows_NT" endlocal
+@rem Execute gradlew
+@rem endlocal doesn't take effect until after the line is parsed and variables are expanded
+@rem which allows us to clear the local environment before executing the java command
+endlocal & "%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -jar "%APP_HOME%\gradle\wrapper\gradle-wrapper.jar" %* & call :exitWithErrorLevel
 
-:omega
+:exitWithErrorLevel
+@rem Use "%COMSPEC%" /c exit to allow operators to work properly in scripts
+"%COMSPEC%" /c exit %ERRORLEVEL%
diff --git a/lib/build.gradle b/lib/build.gradle
index c0a5ce2..249cf92 100644
--- a/lib/build.gradle
+++ b/lib/build.gradle
@@ -27,6 +27,7 @@ def getKeyPassword() {
 
 dependencies {
     testImplementation 'org.junit.jupiter:junit-jupiter:5.7.2'
+    testRuntimeOnly 'org.junit.platform:junit-platform-launcher'
     testImplementation "com.github.tomakehurst:wiremock-jre8:2.32.0"
     testImplementation "org.mockito:mockito-core:3.12.4"
 
@@ -42,6 +43,11 @@ java {
     withSourcesJar()
     sourceCompatibility = JavaVersion.VERSION_1_8
     targetCompatibility = JavaVersion.VERSION_1_8
+    if (project.hasProperty('testJavaVersion')) {
+        toolchain {
+            languageVersion = JavaLanguageVersion.of(project.property('testJavaVersion') as int)
+        }
+    }
 }
 
 tasks.named('test', Test) {
diff --git a/lib/gradle.lockfile b/lib/gradle.lockfile
index cc4d350..f3f0934 100644
--- a/lib/gradle.lockfile
+++ b/lib/gradle.lockfile
@@ -68,6 +68,7 @@ org.junit.jupiter:junit-jupiter-params:5.7.2=testCompileClasspath,testRuntimeCla
 org.junit.jupiter:junit-jupiter:5.7.2=testCompileClasspath,testRuntimeClasspath
 org.junit.platform:junit-platform-commons:1.7.2=testCompileClasspath,testRuntimeClasspath
 org.junit.platform:junit-platform-engine:1.7.2=testRuntimeClasspath
+org.junit.platform:junit-platform-launcher:1.7.2=testRuntimeClasspath
 org.junit:junit-bom:5.7.2=testCompileClasspath,testRuntimeClasspath
 org.mockito:mockito-core:3.12.4=testCompileClasspath,testRuntimeClasspath
 org.objenesis:objenesis:3.2=testCompileClasspath,testRuntimeClasspath