Keycloak Major Version Upgrade: Migration Guide from 21 to 26
Upgrading Keycloak across major versions is one of those tasks that looks simple on paper — download the new release, start it up, let Liquibase handle the database — but reliably creates production incidents when done without preparation. Between versions 21 and 26, Keycloak introduced several breaking changes that affect clustering, theming, SPIs, and configuration format. This guide covers what actually breaks at each version boundary and how to handle it. ...