diff --git a/.github/workflows/cd.yml b/.github/workflows/cd.yml
index b19c9db..cf42865 100644
--- a/.github/workflows/cd.yml
+++ b/.github/workflows/cd.yml
@@ -23,8 +23,7 @@ jobs:
         #          - windows-latest
         #          - macos-latest
         java:
-          - 8
-    #          - 17
+          - '21'
     runs-on: ${{ matrix.os }}
     timeout-minutes: 20
     steps:
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 1296d20..d2818da 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -25,8 +25,7 @@ jobs:
           # pinned to macos-13 due to https://github.com/actions/runner-images/issues/9254
           - macos-13
         java:
-          - 8
-          - 17
+          - '21'
     runs-on: ${{ matrix.os }}
     timeout-minutes: 20
     steps:
diff --git a/.github/workflows/codeql-analysis.yml b/.github/workflows/codeql-analysis.yml
index bf4e27c..1d978a1 100644
--- a/.github/workflows/codeql-analysis.yml
+++ b/.github/workflows/codeql-analysis.yml
@@ -36,6 +36,11 @@ jobs:
     steps:
     - name: Checkout repository
       uses: actions/checkout@v5
+    - name: Set up JDK
+      uses: actions/setup-java@v5.0.0
+      with:
+        distribution: 'zulu'
+        java-version: '21'
 
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 4a1bfa8..89f7f77 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -25,8 +25,7 @@ jobs:
         #          - windows-latest
         #          - macos-latest
         java:
-          - 8
-    #          - 17
+          - '21'
     runs-on: ${{ matrix.os }}
     timeout-minutes: 20
     steps:
diff --git a/build.gradle.kts b/build.gradle.kts
index b24865b..b65d15b 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -6,7 +6,7 @@ rootProject.extra.set("artifactVersion", SimpleDateFormat("yyyy-MM-dd\'T\'HH-mm-
 plugins {
   id("maven-publish")
   id("com.github.ben-manes.versions") version "0.53.0"
-  id("net.ossindex.audit") version "0.4.11"
+  id("org.sonatype.gradle.plugins.scan") version "3.1.4"
   id("io.freefair.maven-central.validate-poms") version "8.14.2"
   id("io.github.gradle-nexus.publish-plugin") version "2.0.0"
 }
@@ -15,6 +15,7 @@ val dependencyVersions = listOf(
   "org.apache.commons:commons-lang3:3.19.0",
   "org.jetbrains:annotations:26.0.2-1",
   libs.junit4,
+  libs.junit5,
 )
 
 val dependencyGroupVersions = mapOf<String, String>(
@@ -35,6 +36,11 @@ subprojects {
   }
 }
 
+ossIndexAudit {
+  username = System.getenv("SONATYPE_INDEX_USERNAME") ?: findProperty("sonatype.index.username")
+  password = System.getenv("SONATYPE_INDEX_PASSWORD") ?: findProperty("sonatype.index.password")
+}
+
 fun findProperty(s: String) = project.findProperty(s) as String?
 
 val isSnapshot = project.version == "unspecified"
diff --git a/engine/build.gradle.kts b/engine/build.gradle.kts
index 3dc4f62..043f9cd 100644
--- a/engine/build.gradle.kts
+++ b/engine/build.gradle.kts
@@ -6,7 +6,7 @@ plugins {
   id("maven-publish")
   id("signing")
   id("com.github.ben-manes.versions")
-  id("net.ossindex.audit")
+  id("org.sonatype.gradle.plugins.scan")
   id("io.freefair.maven-central.validate-poms")
 }
 
@@ -79,6 +79,7 @@ dependencies {
 
   testImplementation("org.spockframework:spock-core:2.3-groovy-4.0")
   testRuntimeOnly("net.bytebuddy:byte-buddy:1.17.7")
+  testRuntimeOnly("org.junit.platform:junit-platform-launcher:1.13.4")
 }
 
 java {
diff --git a/gradle.properties b/gradle.properties
index 650e697..b9dd23b 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -12,3 +12,6 @@ sonatype.staging.url=https://oss.sonatype.org/service/local/staging/deploy/maven
 sonatype.staging.profile.id=
 sonatype.username=
 sonatype.password=
+
+sonatype.index.username=
+sonatype.index.password=
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index 931d85f..4d6294e 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -16,6 +16,7 @@ slf4jVersionrange = "[1.7,3)"
 
 [libraries]
 junit4 = { module = "junit:junit", version = "4.13.2" }
+junit5 = { module = "org.junit:junit-bom", version = "5.13.4" }
 junixsocketCore = { module = "com.kohlschutter.junixsocket:junixsocket-core", version.ref = "junixsocket" }
 junixsocketCommon = { module = "com.kohlschutter.junixsocket:junixsocket-common", version.ref = "junixsocket" }
 kotlin = { module = "org.jetbrains.kotlin:kotlin-stdlib", version.ref = "kotlin" }
diff --git a/gradle/wrapper/gradle-wrapper.jar b/gradle/wrapper/gradle-wrapper.jar
index 1b33c55..8bdaf60 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 78cb6e1..6a38a8c 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,7 +1,7 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionSha256Sum=bd71102213493060956ec229d946beee57158dbd89d0e62b91bca0fa2c5f3531
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.14.3-bin.zip
+distributionSha256Sum=a17ddd85a26b6a7f5ddb71ff8b05fc5104c0202c6e64782429790c933686c806
+distributionUrl=https\://services.gradle.org/distributions/gradle-9.1.0-bin.zip
 networkTimeout=10000
 validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME
diff --git a/gradlew b/gradlew
index 23d15a9..adff685 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.
@@ -114,7 +114,6 @@ case "$( uname )" in                #(
   NONSTOP* )        nonstop=true ;;
 esac
 
-CLASSPATH="\\\"\\\""
 
 
 # Determine the Java command to use to start the JVM.
@@ -172,7 +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" )
 
@@ -212,7 +210,6 @@ DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
 
 set -- \
         "-Dorg.gradle.appname=$APP_BASE_NAME" \
-        -classpath "$CLASSPATH" \
         -jar "$APP_HOME/gradle/wrapper/gradle-wrapper.jar" \
         "$@"
 
diff --git a/gradlew.bat b/gradlew.bat
index db3a6ac..c4bdd3a 100644
--- a/gradlew.bat
+++ b/gradlew.bat
@@ -70,11 +70,10 @@ goto fail
 :execute
 @rem Setup the command line
 
-set CLASSPATH=
 
 
 @rem Execute Gradle
-"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" -jar "%APP_HOME%\gradle\wrapper\gradle-wrapper.jar" %*
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -jar "%APP_HOME%\gradle\wrapper\gradle-wrapper.jar" %*
 
 :end
 @rem End local scope for the variables with windows NT shell
diff --git a/integrationtest/build.gradle.kts b/integrationtest/build.gradle.kts
index 6e054dc..ea813e9 100644
--- a/integrationtest/build.gradle.kts
+++ b/integrationtest/build.gradle.kts
@@ -1,7 +1,7 @@
 plugins {
   groovy
   id("com.github.ben-manes.versions")
-  id("net.ossindex.audit")
+  id("org.sonatype.gradle.plugins.scan")
 }
 
 java {
@@ -55,6 +55,7 @@ dependencies {
   testRuntimeOnly(libs.logback)
   testImplementation("org.spockframework:spock-core:2.3-groovy-4.0")
   testRuntimeOnly("net.bytebuddy:byte-buddy:1.17.7")
+  testRuntimeOnly("org.junit.platform:junit-platform-launcher:1.13.4")
 }
 tasks.check.get().shouldRunAfter(project(":engine").tasks.check)
 
diff --git a/settings.gradle.kts b/settings.gradle.kts
index 23d8a66..fc8737d 100644
--- a/settings.gradle.kts
+++ b/settings.gradle.kts
@@ -3,5 +3,5 @@ include("engine", "integrationtest")
 
 // https://docs.gradle.org/current/userguide/toolchains.html#sub:download_repositories
 plugins {
-  id("org.gradle.toolchains.foojay-resolver-convention") version "0.10.0"
+  id("org.gradle.toolchains.foojay-resolver-convention") version "1.0.0"
 }