diff --git a/packages/java/tests/pom.xml b/packages/java/tests/pom.xml
index 2f6f84c782..48c8e617a7 100644
--- a/packages/java/tests/pom.xml
+++ b/packages/java/tests/pom.xml
@@ -30,6 +30,9 @@
         <!-- make sure we do not leave webpack-dev-server running after IT -->
         <vaadin.reuseDevServer>false</vaadin.reuseDevServer>
 
+        <!-- enable React 19 feature flag by default -->
+        <vaadin.experimental.react19>true</vaadin.experimental.react19>
+
         <!-- Used in the tests, should be overridden for each module to support
     concurrent running of test modules. -->
         <server.port>8888</server.port>
@@ -139,6 +142,18 @@
 
     <build>
         <plugins>
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>properties-maven-plugin</artifactId>
+                <version>${properties-maven-plugin.version}</version>
+                <executions>
+                    <execution>
+                        <goals>
+                            <goal>set-system-properties</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-failsafe-plugin</artifactId>
@@ -252,16 +267,26 @@
                             </goals>
                             <configuration>
                                 <properties>
-                                    <vaadin.reuseDevServer>${vaadin.reuseDevServer}</vaadin.reuseDevServer>
-                  <vaadin.devmode.liveReload.enabled>
-                                    ${vaadin.devmode.liveReload.enabled}</vaadin.devmode.liveReload.enabled>
-                  <vaadin.allow.appshell.annotations>
-                                    ${vaadin.allow.appshell.annotations}</vaadin.allow.appshell.annotations>
-
-                  <jetty.scantrigger>
-                                    ${jetty.scantrigger}</jetty.scantrigger>-->                   <!-- Allow test clients not on localhost to connect to Vite-->
-                  <vaadin.devmode.vite.options>
-                                    ${vaadin.devmode.vite.options}</vaadin.devmode.vite.options>
+                                    <jetty.scantrigger>
+                                        ${jetty.scantrigger}
+                                    </jetty.scantrigger>
+                                    <vaadin.reuseDevServer>
+                                        ${vaadin.reuseDevServer}
+                                    </vaadin.reuseDevServer>
+                                    <vaadin.devmode.liveReload.enabled>
+                                        ${vaadin.devmode.liveReload.enabled}
+                                    </vaadin.devmode.liveReload.enabled>
+                                    <vaadin.allow.appshell.annotations>
+                                        ${vaadin.allow.appshell.annotations}
+                                    </vaadin.allow.appshell.annotations>
+                                    <!-- Allow test clients not on localhost
+                                    to connect to Vite -->
+                                    <vaadin.devmode.vite.options>
+                                        ${vaadin.devmode.vite.options}
+                                    </vaadin.devmode.vite.options>
+                                    <vaadin.experimental.react19>
+                                        ${vaadin.experimental.react19}
+                                    </vaadin.experimental.react19>
                                 </properties>
                             </configuration>
                         </execution>
@@ -331,5 +356,15 @@
             </modules>
         </profile>
 
+        <profile>
+            <id>react-18</id>
+            <properties>
+                <vaadin.experimental.react19>false</vaadin.experimental.react19>
+            </properties>
+            <modules>
+                <module>spring</module>
+            </modules>
+        </profile>
+
     </profiles>
 </project>
diff --git a/packages/java/tests/spring/pom.xml b/packages/java/tests/spring/pom.xml
index dd6294bdc6..bc0c696a57 100644
--- a/packages/java/tests/spring/pom.xml
+++ b/packages/java/tests/spring/pom.xml
@@ -130,6 +130,44 @@
                             </goals>
                         </execution>
                     </executions>
+                    <configuration>
+                        <systemPropertyVariables>
+                            <vaadin.reuseDevServer>
+                                ${vaadin.reuseDevServer}
+                            </vaadin.reuseDevServer>
+                            <vaadin.devmode.liveReload.enabled>
+                                ${vaadin.devmode.liveReload.enabled}
+                            </vaadin.devmode.liveReload.enabled>
+                            <vaadin.allow.appshell.annotations>
+                                ${vaadin.allow.appshell.annotations}
+                            </vaadin.allow.appshell.annotations>
+                            <!-- Allow test clients not on localhost
+                            to connect to Vite -->
+                            <vaadin.devmode.vite.options>
+                                ${vaadin.devmode.vite.options}
+                            </vaadin.devmode.vite.options>
+                            <vaadin.experimental.react19>
+                                ${vaadin.experimental.react19}
+                            </vaadin.experimental.react19>
+                            <vaadin.reuseDevServer>
+                                ${vaadin.reuseDevServer}
+                            </vaadin.reuseDevServer>
+                            <vaadin.devmode.liveReload.enabled>
+                                ${vaadin.devmode.liveReload.enabled}
+                            </vaadin.devmode.liveReload.enabled>
+                            <vaadin.allow.appshell.annotations>
+                                ${vaadin.allow.appshell.annotations}
+                            </vaadin.allow.appshell.annotations>
+                            <!-- Allow test clients not on localhost
+                            to connect to Vite-->
+                            <vaadin.devmode.vite.options>
+                                ${vaadin.devmode.vite.options}
+                            </vaadin.devmode.vite.options>
+                            <vaadin.experimental.react19>
+                                ${vaadin.experimental.react19}
+                            </vaadin.experimental.react19>
+                        </systemPropertyVariables>
+                    </configuration>
                 </plugin>
             </plugins>
         </pluginManagement>
@@ -231,6 +269,16 @@
             </modules>
         </profile>
 
+        <profile>
+            <id>react-18</id>
+            <modules>
+                <module>no-endpoints</module>
+                <module>react-grid-test</module>
+                <module>react-i18n</module>
+                <module>react-signals</module>
+            </modules>
+        </profile>
+
         <profile>
             <id>native</id>
             <modules>
diff --git a/packages/java/tests/spring/react-grid-test/src/main/resources/vaadin-featureflags.properties b/packages/java/tests/spring/react-grid-test/src/main/resources/vaadin-featureflags.properties
index 80f7397d52..1cdc976662 100644
--- a/packages/java/tests/spring/react-grid-test/src/main/resources/vaadin-featureflags.properties
+++ b/packages/java/tests/spring/react-grid-test/src/main/resources/vaadin-featureflags.properties
@@ -1,2 +1,4 @@
+# Enable Hilla I18n feature flag so that we can test it
+com.vaadin.experimental.hillaI18n=true
 # React 19 (default in Vaadin 25)
 com.vaadin.experimental.react19=true