diff --git a/build/optaplanner-build-parent/pom.xml b/build/optaplanner-build-parent/pom.xml
index f018154480f..2aa8eca82d0 100644
--- a/build/optaplanner-build-parent/pom.xml
+++ b/build/optaplanner-build-parent/pom.xml
@@ -46,7 +46,7 @@
     <version.org.apache.logging.log4j>2.22.1</version.org.apache.logging.log4j>
     <version.com.thoughtworks.xstream>1.4.20</version.com.thoughtworks.xstream>
     <version.io.quarkiverse.operatorsdk>6.6.7</version.io.quarkiverse.operatorsdk>
-    <version.io.quarkus>3.8.6</version.io.quarkus>
+    <version.io.quarkus>3.15.1</version.io.quarkus>
     <version.org.apache.commons.math3>3.6.1</version.org.apache.commons.math3>
     <version.org.apache.commons.text>1.11.0</version.org.apache.commons.text>
     <version.org.apache.openjpa>4.0.0</version.org.apache.openjpa>
diff --git a/optaplanner-quarkus-integration/optaplanner-quarkus-benchmark/deployment/pom.xml b/optaplanner-quarkus-integration/optaplanner-quarkus-benchmark/deployment/pom.xml
index 9ec3c94eda6..b4d9efe999e 100644
--- a/optaplanner-quarkus-integration/optaplanner-quarkus-benchmark/deployment/pom.xml
+++ b/optaplanner-quarkus-integration/optaplanner-quarkus-benchmark/deployment/pom.xml
@@ -108,6 +108,9 @@
               <version>${version.io.quarkus}</version>
             </path>
           </annotationProcessorPaths>
+          <compilerArgs>
+            <arg>-AlegacyConfigRoot=true</arg>
+          </compilerArgs>
         </configuration>
       </plugin>
       <plugin>
diff --git a/optaplanner-quarkus-integration/optaplanner-quarkus-benchmark/runtime/pom.xml b/optaplanner-quarkus-integration/optaplanner-quarkus-benchmark/runtime/pom.xml
index 2dcbb2d5a5d..6ea95c3f30c 100644
--- a/optaplanner-quarkus-integration/optaplanner-quarkus-benchmark/runtime/pom.xml
+++ b/optaplanner-quarkus-integration/optaplanner-quarkus-benchmark/runtime/pom.xml
@@ -96,6 +96,9 @@
               <version>${version.io.quarkus}</version>
             </path>
           </annotationProcessorPaths>
+          <compilerArgs>
+            <arg>-AlegacyConfigRoot=true</arg>
+          </compilerArgs>
         </configuration>
       </plugin>
       <plugin>
diff --git a/optaplanner-quarkus-integration/optaplanner-quarkus-jackson/deployment/pom.xml b/optaplanner-quarkus-integration/optaplanner-quarkus-jackson/deployment/pom.xml
index 950f767c91e..3da3593b777 100644
--- a/optaplanner-quarkus-integration/optaplanner-quarkus-jackson/deployment/pom.xml
+++ b/optaplanner-quarkus-integration/optaplanner-quarkus-jackson/deployment/pom.xml
@@ -73,6 +73,9 @@
               <version>${version.io.quarkus}</version>
             </path>
           </annotationProcessorPaths>
+          <compilerArgs>
+            <arg>-AlegacyConfigRoot=true</arg>
+          </compilerArgs>
         </configuration>
       </plugin>
     </plugins>
diff --git a/optaplanner-quarkus-integration/optaplanner-quarkus-jackson/runtime/pom.xml b/optaplanner-quarkus-integration/optaplanner-quarkus-jackson/runtime/pom.xml
index f42a2da5be1..fcbb3ec9abb 100644
--- a/optaplanner-quarkus-integration/optaplanner-quarkus-jackson/runtime/pom.xml
+++ b/optaplanner-quarkus-integration/optaplanner-quarkus-jackson/runtime/pom.xml
@@ -91,6 +91,9 @@
               <version>${version.io.quarkus}</version>
             </path>
           </annotationProcessorPaths>
+          <compilerArgs>
+            <arg>-AlegacyConfigRoot=true</arg>
+          </compilerArgs>
         </configuration>
       </plugin>
       <plugin>
diff --git a/optaplanner-quarkus-integration/optaplanner-quarkus-jsonb/deployment/pom.xml b/optaplanner-quarkus-integration/optaplanner-quarkus-jsonb/deployment/pom.xml
index 353abd04b76..eae3edb9336 100644
--- a/optaplanner-quarkus-integration/optaplanner-quarkus-jsonb/deployment/pom.xml
+++ b/optaplanner-quarkus-integration/optaplanner-quarkus-jsonb/deployment/pom.xml
@@ -73,6 +73,9 @@
               <version>${version.io.quarkus}</version>
             </path>
           </annotationProcessorPaths>
+          <compilerArgs>
+            <arg>-AlegacyConfigRoot=true</arg>
+          </compilerArgs>
         </configuration>
       </plugin>
     </plugins>
diff --git a/optaplanner-quarkus-integration/optaplanner-quarkus-jsonb/runtime/pom.xml b/optaplanner-quarkus-integration/optaplanner-quarkus-jsonb/runtime/pom.xml
index e1d07f03355..eaabc990ccb 100644
--- a/optaplanner-quarkus-integration/optaplanner-quarkus-jsonb/runtime/pom.xml
+++ b/optaplanner-quarkus-integration/optaplanner-quarkus-jsonb/runtime/pom.xml
@@ -92,6 +92,9 @@
               <version>${version.io.quarkus}</version>
             </path>
           </annotationProcessorPaths>
+          <compilerArgs>
+            <arg>-AlegacyConfigRoot=true</arg>
+          </compilerArgs>
         </configuration>
       </plugin>
     </plugins>
diff --git a/optaplanner-quarkus-integration/optaplanner-quarkus/deployment/pom.xml b/optaplanner-quarkus-integration/optaplanner-quarkus/deployment/pom.xml
index 139cd6f8809..7be68161a03 100644
--- a/optaplanner-quarkus-integration/optaplanner-quarkus/deployment/pom.xml
+++ b/optaplanner-quarkus-integration/optaplanner-quarkus/deployment/pom.xml
@@ -106,6 +106,9 @@
               <version>${version.io.quarkus}</version>
             </path>
           </annotationProcessorPaths>
+          <compilerArgs>
+            <arg>-AlegacyConfigRoot=true</arg>
+          </compilerArgs>
         </configuration>
       </plugin>
       <plugin>
diff --git a/optaplanner-quarkus-integration/optaplanner-quarkus/runtime/pom.xml b/optaplanner-quarkus-integration/optaplanner-quarkus/runtime/pom.xml
index e3420bf10b4..4f70512453d 100644
--- a/optaplanner-quarkus-integration/optaplanner-quarkus/runtime/pom.xml
+++ b/optaplanner-quarkus-integration/optaplanner-quarkus/runtime/pom.xml
@@ -104,6 +104,9 @@
               <version>${version.io.quarkus}</version>
             </path>
           </annotationProcessorPaths>
+          <compilerArgs>
+            <arg>-AlegacyConfigRoot=true</arg>
+          </compilerArgs>
         </configuration>
       </plugin>
       <plugin>