Developers moving from Java 21 to Java 25 may find that changing the version in pom.xml is not enough to keep an application running. The Spring IO team has compiled a set of real incompatibilities and checks worth completing before the migration begins. On JDK 25, older annotation processors may no longer start, which can prevent a build from completing. Previously accepted JVM options may also fail, causing errors during startup. Changes in how dates are parsed can alter application behavior without producing an obvious build-time warning. Some failures appear immediately after the upgrade, while others remain hidden until a particular code path is used. The translated guidance therefore recommends testing compatibility during the build and startup process, then exercising the application’s main behavior before making Java 25 the production version. Teams should also check less frequently used features because delayed failures can be harder to diagnose than an immediate crash.