diff --git a/.github/workflows/artifactory-milestone-release.yml b/.github/workflows/artifactory-milestone-release.yml
index 290d73c0f53..6482b462543 100644
--- a/.github/workflows/artifactory-milestone-release.yml
+++ b/.github/workflows/artifactory-milestone-release.yml
@@ -18,7 +18,7 @@ jobs:
       - name: Set up JDK
         uses: actions/setup-java@v4
         with:
-          java-version: '25'
+          java-version: '21'
           distribution: 'temurin'
           cache: 'maven'
 
diff --git a/.github/workflows/continuous-integration.yml b/.github/workflows/continuous-integration.yml
index ae174fb62f5..ca4792882f2 100644
--- a/.github/workflows/continuous-integration.yml
+++ b/.github/workflows/continuous-integration.yml
@@ -48,7 +48,7 @@ jobs:
       - name: Set up JDK
         uses: actions/setup-java@v4
         with:
-          java-version: '25'
+          java-version: '21'
           distribution: 'temurin'
           cache: 'maven'
 
diff --git a/.github/workflows/documentation-upload.yml b/.github/workflows/documentation-upload.yml
index 7e67f3e2b80..b07932e9bc3 100644
--- a/.github/workflows/documentation-upload.yml
+++ b/.github/workflows/documentation-upload.yml
@@ -21,7 +21,7 @@ jobs:
       - name: Set up JDK
         uses: actions/setup-java@v4
         with:
-          java-version: '25'
+          java-version: '21'
           distribution: 'temurin'
           cache: 'maven'
 
diff --git a/.github/workflows/fast-continuous-integration.yml b/.github/workflows/fast-continuous-integration.yml
index b72fbcedb45..cc9dce0f982 100644
--- a/.github/workflows/fast-continuous-integration.yml
+++ b/.github/workflows/fast-continuous-integration.yml
@@ -30,7 +30,7 @@ jobs:
       - name: Set up JDK
         uses: actions/setup-java@v4
         with:
-          java-version: '25'
+          java-version: '21'
           distribution: 'temurin'
           cache: 'maven'
 
@@ -65,7 +65,7 @@ jobs:
       - name: Set up JDK
         uses: actions/setup-java@v4
         with:
-          java-version: '25'
+          java-version: '21'
           distribution: 'temurin'
           cache: 'maven'
 
@@ -102,7 +102,7 @@ jobs:
       - name: Set up JDK
         uses: actions/setup-java@v4
         with:
-          java-version: '25'
+          java-version: '21'
           distribution: 'temurin'
           cache: 'maven'
 
@@ -139,7 +139,7 @@ jobs:
       - name: Set up JDK
         uses: actions/setup-java@v4
         with:
-          java-version: '25'
+          java-version: '21'
           distribution: 'temurin'
           cache: 'maven'
 
@@ -176,7 +176,7 @@ jobs:
       - name: Set up JDK
         uses: actions/setup-java@v4
         with:
-          java-version: '25'
+          java-version: '21'
           distribution: 'temurin'
           cache: 'maven'
 
@@ -219,7 +219,7 @@ jobs:
       - name: Set up JDK
         uses: actions/setup-java@v4
         with:
-          java-version: '25'
+          java-version: '21'
           distribution: 'temurin'
           cache: 'maven'
 
@@ -248,7 +248,7 @@ jobs:
       - name: Set up JDK
         uses: actions/setup-java@v4
         with:
-          java-version: '25'
+          java-version: '21'
           distribution: 'temurin'
           cache: 'maven'
 
diff --git a/.github/workflows/main-push-fast.yml b/.github/workflows/main-push-fast.yml
index a19ecf322ee..15e3bfc9603 100644
--- a/.github/workflows/main-push-fast.yml
+++ b/.github/workflows/main-push-fast.yml
@@ -53,7 +53,7 @@ jobs:
 
       - uses: actions/setup-java@v4
         with:
-          java-version: '25'
+          java-version: '21'
           distribution: 'temurin'
           # cache: 'maven'  # Disabled for fast workflow - reduces post-job noise
 
diff --git a/.github/workflows/maintenance-fast.yml b/.github/workflows/maintenance-fast.yml
index 1a903df2144..4e3d0541d9b 100644
--- a/.github/workflows/maintenance-fast.yml
+++ b/.github/workflows/maintenance-fast.yml
@@ -20,7 +20,7 @@ jobs:
 
       - uses: actions/setup-java@v4
         with:
-          java-version: '25'
+          java-version: '21'
           distribution: 'temurin'
           cache: 'maven'
 
diff --git a/.github/workflows/pr-check.yml b/.github/workflows/pr-check.yml
index 23a52bb0902..3dd1f76b1db 100644
--- a/.github/workflows/pr-check.yml
+++ b/.github/workflows/pr-check.yml
@@ -17,7 +17,7 @@ jobs:
       - name: Set up JDK
         uses: actions/setup-java@v4
         with:
-          java-version: '25'
+          java-version: '21'
           distribution: 'temurin'
           cache: 'maven'
 
diff --git a/.github/workflows/release-notes-generation.yml b/.github/workflows/release-notes-generation.yml
index 5b53cc8b0b4..a6ebe546504 100644
--- a/.github/workflows/release-notes-generation.yml
+++ b/.github/workflows/release-notes-generation.yml
@@ -26,7 +26,7 @@ jobs:
       - name: Set up JDK
         uses: actions/setup-java@v4
         with:
-          java-version: '25'
+          java-version: '21'
           distribution: 'temurin'
 
       - name: Prepare configuration file
diff --git a/.sdkmanrc b/.sdkmanrc
new file mode 100644
index 00000000000..5a6900dd570
--- /dev/null
+++ b/.sdkmanrc
@@ -0,0 +1,3 @@
+# Enable auto-env through the sdkman_auto_env config
+# Add key=value pairs of SDKs to use below
+java=21.0.9-tem
diff --git a/README.md b/README.md
index 242a8f2c122..a8a0a11785d 100644
--- a/README.md
+++ b/README.md
@@ -71,7 +71,7 @@ To clone it you have to either:
 
 ## Building
 
-The project targets and build artifacts compatible with Java 17+, but requires a JDK 25+
+The project targets and build artifacts compatible with Java 17+, but requires JDK 21
 to build. This is enforced by the maven enforcer plugin.
 
 To build with running unit tests
diff --git a/pom.xml b/pom.xml
index 1a1b458db13..cb029fd1296 100644
--- a/pom.xml
+++ b/pom.xml
@@ -274,7 +274,6 @@
 		<maven.compiler.source>${java.version}</maven.compiler.source>
 		<maven.compiler.target>${java.version}</maven.compiler.target>
 		<kotlin.compiler.jvmTarget>${java.version}</kotlin.compiler.jvmTarget>
-		<kotlin.compiler.version>2.2.21</kotlin.compiler.version>
 
 		<!-- production dependencies -->
 		<spring-boot.version>4.0.0</spring-boot.version>
@@ -340,7 +339,7 @@
 		<okhttp3.version>4.12.0</okhttp3.version>
 		<rest-assured-bom.version>5.5.6</rest-assured-bom.version>
 		<json-unit-assertj.version>4.1.0</json-unit-assertj.version>
-		
+
 		<!-- MCP-->
 		<mcp.sdk.version>0.18.0-SNAPSHOT</mcp.sdk.version>
 		<mcp-annotations.version>0.9.0-SNAPSHOT</mcp-annotations.version>
@@ -351,7 +350,7 @@
 		<maven-enforcer-plugin.version>3.6.2</maven-enforcer-plugin.version>
 		<!-- The version (range) of the JDK we want to use to compile.
 			This is different from ${java.version} which we use as -release target. -->
-		<compiler.jdk.version>[25,)</compiler.jdk.version>
+		<compiler.jdk.version>[21.0.8,)</compiler.jdk.version>
 		<maven-surefire-plugin.version>3.1.2</maven-surefire-plugin.version>
 		<maven-failsafe-plugin.version>3.5.2</maven-failsafe-plugin.version>
 		<maven-javadoc-plugin.version>3.5.0</maven-javadoc-plugin.version>
@@ -422,10 +421,12 @@
 			<plugin>
 				<groupId>org.jetbrains.kotlin</groupId>
 				<artifactId>kotlin-maven-plugin</artifactId>
-				<version>${kotlin.compiler.version}</version>
+				<version>${kotlin.version}</version>
 				<configuration>
 					<jvmTarget>${java.version}</jvmTarget>
 					<javaParameters>true</javaParameters>
+					<apiVersion>2.2</apiVersion>
+					<languageVersion>2.2</languageVersion>
 				</configuration>
 				<executions>
 					<execution>
@@ -462,9 +463,6 @@
 					<release>${java.version}</release>
 					<compilerArgs>
 						<arg>-parameters</arg>
-						<arg>-XDcompilePolicy=simple</arg>
-						<arg>--should-stop=ifError=FLOW</arg>
-						<arg>-Xplugin:ErrorProne -XepDisableAllChecks -Xep:NullAway:ERROR -XepOpt:NullAway:OnlyNullMarked -XepOpt:NullAway:JSpecifyMode=true</arg>
 					</compilerArgs>
 					<annotationProcessorPaths>
 						<path>
@@ -496,6 +494,15 @@
 						<goals>
 							<goal>compile</goal>
 						</goals>
+						<configuration>
+							<compilerArgs>
+								<arg>-XDcompilePolicy=simple</arg>
+								<!-- The following arg won't be necessary with JDK25+ -->
+								<arg>-XDaddTypeAnnotationsToSymbol=true</arg>
+								<arg>--should-stop=ifError=FLOW</arg>
+								<arg>-Xplugin:ErrorProne -XepDisableAllChecks -Xep:NullAway:ERROR -XepOpt:NullAway:OnlyNullMarked -XepOpt:NullAway:JSpecifyMode=true</arg>
+							</compilerArgs>
+						</configuration>
 					</execution>
 					<execution>
 						<id>java-test-compile</id>