stackabletech · sbernauer · Sep 29, 2026 · Sep 29, 2026
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -57,6 +57,9 @@ All notable changes to this project will be documented in this file.
 - A KRaft cluster without a `controllers` role is now rejected during validation.
   Previously, the operator would create a cluster consisting only of `brokers` which would never
   become healthy ([#1010]).
+- `spec.clusterConfig.metadataManager` now uses PascalCase values (`ZooKeeper` and `KRaft`) as per
+  Kubernetes conventions. The lowercase values `zookeeper` and `kraft` are deprecated, but are still
+  accepted for backwards compatibility and may be removed in a future release ([#1034]).
 
 ### Removed
 
@@ -79,6 +82,7 @@ All notable changes to this project will be documented in this file.
 [#1021]: https://github.com/stackabletech/kafka-operator/pull/1021
 [#1022]: https://github.com/stackabletech/kafka-operator/pull/1022
 [#1024]: https://github.com/stackabletech/kafka-operator/pull/1024
+[#1034]: https://github.com/stackabletech/kafka-operator/pull/1034
 
 ## [26.7.0] - 2026-07-21
 

diff --git a/docs/modules/kafka/examples/kraft_migration/01-setup.yaml b/docs/modules/kafka/examples/kraft_migration/01-setup.yaml
@@ -84,7 +84,7 @@ spec:
     productVersion: 3.9.2
     pullPolicy: IfNotPresent
   clusterConfig:
-    metadataManager: zookeeper
+    metadataManager: ZooKeeper
     brokerIdPodConfigMapName: broker-ids
     authentication:
       - authenticationClass: kafka-client-auth-tls

diff --git a/docs/modules/kafka/examples/kraft_migration/02-start-controllers.yaml b/docs/modules/kafka/examples/kraft_migration/02-start-controllers.yaml
@@ -9,7 +9,7 @@ spec:
     productVersion: 3.9.2
     pullPolicy: IfNotPresent
   clusterConfig:
-    metadataManager: zookeeper
+    metadataManager: ZooKeeper
     authentication:
       - authenticationClass: kafka-client-auth-tls
     tls:

diff --git a/docs/modules/kafka/examples/kraft_migration/03-migrate-metadata.yaml b/docs/modules/kafka/examples/kraft_migration/03-migrate-metadata.yaml
@@ -9,7 +9,7 @@ spec:
     productVersion: 3.9.2
     pullPolicy: IfNotPresent
   clusterConfig:
-    metadataManager: zookeeper
+    metadataManager: ZooKeeper
     authentication:
       - authenticationClass: kafka-client-auth-tls
     tls:

diff --git a/docs/modules/kafka/examples/kraft_migration/04-migrate-brokers.yaml b/docs/modules/kafka/examples/kraft_migration/04-migrate-brokers.yaml
@@ -9,7 +9,7 @@ spec:
     productVersion: 3.9.2
     pullPolicy: IfNotPresent
   clusterConfig:
-    metadataManager: zookeeper
+    metadataManager: ZooKeeper
     authentication:
       - authenticationClass: kafka-client-auth-tls
     tls:

diff --git a/docs/modules/kafka/examples/kraft_migration/05-kraft-mode.yaml b/docs/modules/kafka/examples/kraft_migration/05-kraft-mode.yaml
@@ -9,7 +9,7 @@ spec:
     productVersion: 3.9.2
     pullPolicy: IfNotPresent
   clusterConfig:
-    metadataManager: kraft
+    metadataManager: KRaft
     authentication:
       - authenticationClass: kafka-client-auth-tls
     tls:

diff --git a/docs/modules/kafka/examples/mirror_maker/01-setup-source.yaml b/docs/modules/kafka/examples/mirror_maker/01-setup-source.yaml
@@ -74,7 +74,7 @@ spec:
     productVersion: 3.9.2
     pullPolicy: IfNotPresent
   clusterConfig:
-    metadataManager: zookeeper
+    metadataManager: ZooKeeper
     authentication:
       - authenticationClass: source-client-auth
     tls:

diff --git a/docs/modules/kafka/examples/mirror_maker/02-setup-target.yaml b/docs/modules/kafka/examples/mirror_maker/02-setup-target.yaml
@@ -44,7 +44,7 @@ spec:
     productVersion: 3.9.2
     pullPolicy: IfNotPresent
   clusterConfig:
-    metadataManager: kraft
+    metadataManager: KRaft
     authentication:
       - authenticationClass: target-client-auth
     tls:

diff --git a/docs/modules/kafka/pages/usage-guide/kraft-controller.adoc b/docs/modules/kafka/pages/usage-guide/kraft-controller.adoc
@@ -29,7 +29,7 @@ metadata:
   name: kafka
 spec:
   clusterConfig:
-    metadataManager: kraft
+    metadataManager: KRaft
   image:
     productVersion: "3.9.2"
   brokers:

diff --git a/extra/crds.yaml b/extra/crds.yaml
@@ -1030,16 +1030,17 @@ spec:
 
                       IMPORTANT: This property will be removed as soon as Kafka 3.x support is dropped.
 
-                      Possible values are `zookeeper` and `kraft`.
+                      Possible values are `ZooKeeper` and `KRaft`. The lowercase values `zookeeper` and `kraft`
+                      are deprecated, but still accepted.
 
                       If not set, defaults to:
 
-                      - `zookeeper` for Kafka versions below `4.0.0`.
-                      - `kraft` for Kafka versions `4.0.0` and higher.
+                      - `ZooKeeper` for Kafka versions below `4.0.0`.
+                      - `KRaft` for Kafka versions `4.0.0` and higher.
 
-                      Using `zookeeper` for Kafka versions `4.0.0` and higher is not supported.
+                      Using `ZooKeeper` for Kafka versions `4.0.0` and higher is not supported.
 
-                      When set to `kraft`, the operator will perform the following actions:
+                      When set to `KRaft`, the operator will perform the following actions:
 
                       * Generate the Kafka cluster id.
                       * Assign broker roles and configure controller quorum voters in the `broker.properties` files.
@@ -1051,6 +1052,8 @@ spec:
                       This property is also useful when migrating from ZooKeeper to Kraft mode because it permits the operator
                       to reconcile controllers while still using ZooKeeper for brokers.
                     enum:
+                    - ZooKeeper
+                    - KRaft
                     - zookeeper
                     - kraft
                     - null

diff --git a/rust/operator-binary/src/controller/build/mod.rs b/rust/operator-binary/src/controller/build/mod.rs
@@ -267,7 +267,7 @@ mod tests {
               image:
                 productVersion: 3.9.2
               clusterConfig:
-                metadataManager: kraft
+                metadataManager: KRaft
               controllers:
                 roleGroups:
                   default:
@@ -295,7 +295,7 @@ mod tests {
               image:
                 productVersion: 3.9.2
               clusterConfig:
-                metadataManager: kraft
+                metadataManager: KRaft
               controllers:
                 roleGroups:
                   default:

diff --git a/rust/operator-binary/src/controller/build/resource/statefulset.rs b/rust/operator-binary/src/controller/build/resource/statefulset.rs
@@ -1030,7 +1030,7 @@ mod tests {
               image:
                 productVersion: 3.9.2
               clusterConfig:
-                metadataManager: kraft
+                metadataManager: KRaft
               controllers:
                 roleGroups:
                   default:

diff --git a/rust/operator-binary/src/controller/validate.rs b/rust/operator-binary/src/controller/validate.rs
@@ -485,7 +485,7 @@ mod tests {
               image:
                 productVersion: 3.9.2
               clusterConfig:
-                metadataManager: kraft
+                metadataManager: KRaft
               controllers:
                 roleGroups:
                   default:
@@ -587,7 +587,7 @@ mod tests {
               image:
                 productVersion: 3.9.2
               clusterConfig:
-                metadataManager: kraft
+                metadataManager: KRaft
               controllers:
                 roleGroups:
                   default:
@@ -657,7 +657,7 @@ mod tests {
               image:
                 productVersion: 3.9.2
               clusterConfig:
-                metadataManager: kraft
+                metadataManager: KRaft
               controllers:
                 roleGroups:
                   a:
@@ -699,7 +699,7 @@ mod tests {
               image:
                 productVersion: 3.9.2
               clusterConfig:
-                metadataManager: kraft
+                metadataManager: KRaft
               controllers:
                 roleGroups:
                   default:

diff --git a/rust/operator-binary/src/crd/mod.rs b/rust/operator-binary/src/crd/mod.rs
@@ -194,16 +194,17 @@ pub mod versioned {
         ///
         /// IMPORTANT: This property will be removed as soon as Kafka 3.x support is dropped.
         ///
-        /// Possible values are `zookeeper` and `kraft`.
+        /// Possible values are `ZooKeeper` and `KRaft`. The lowercase values `zookeeper` and `kraft`
+        /// are deprecated, but still accepted.
         ///
         /// If not set, defaults to:
         ///
-        /// - `zookeeper` for Kafka versions below `4.0.0`.
-        /// - `kraft` for Kafka versions `4.0.0` and higher.
+        /// - `ZooKeeper` for Kafka versions below `4.0.0`.
+        /// - `KRaft` for Kafka versions `4.0.0` and higher.
         ///
-        /// Using `zookeeper` for Kafka versions `4.0.0` and higher is not supported.
+        /// Using `ZooKeeper` for Kafka versions `4.0.0` and higher is not supported.
         ///
-        /// When set to `kraft`, the operator will perform the following actions:
+        /// When set to `KRaft`, the operator will perform the following actions:
         ///
         /// * Generate the Kafka cluster id.
         /// * Assign broker roles and configure controller quorum voters in the `broker.properties` files.
@@ -365,9 +366,15 @@ pub struct KafkaClusterStatus {
     Serialize,
     EnumString,
 )]
-#[serde(rename_all = "lowercase")]
+#[serde(rename_all = "PascalCase")]
+// schemars ignores `#[serde(alias)]` (https://github.com/GREsau/schemars/issues/338), so we need to
+// list the aliases in the schema manually. Otherwise the API server rejects them.
+#[schemars(extend("enum" = ["ZooKeeper", "KRaft", "zookeeper", "kraft"]))]
 pub enum MetadataManager {
+    // The lowercase aliases are deprecated and only kept for backwards compatibility.
+    #[serde(alias = "zookeeper")]
     ZooKeeper,
+    #[serde(alias = "kraft")]
     KRaft,
 }
 
@@ -669,7 +676,7 @@ mod tests {
                   reconciliationPaused: false
                   stopped: true
                 clusterConfig:
-                  metadataManager: kraft
+                  metadataManager: KRaft
                   authentication:
                     - authenticationClass: my-kerberos
                   authorization:

diff --git a/tests/templates/kuttl/kraft-kerberos/20-install-kafka.yaml.j2 b/tests/templates/kuttl/kraft-kerberos/20-install-kafka.yaml.j2
@@ -29,7 +29,7 @@ commands:
           pullPolicy: IfNotPresent
         clusterConfig:
           # KRaft: metadata is managed by the controllers role, no ZooKeeper involved.
-          metadataManager: kraft
+          metadataManager: KRaft
           authentication:
             - authenticationClass: kerberos-auth-$NAMESPACE
           tls:

diff --git a/tests/templates/kuttl/kraft-kerberos/60-scale-controller-up.yaml.j2 b/tests/templates/kuttl/kraft-kerberos/60-scale-controller-up.yaml.j2
@@ -21,7 +21,7 @@ commands:
           pullPolicy: IfNotPresent
         clusterConfig:
           # KRaft: metadata is managed by the controllers role, no ZooKeeper involved.
-          metadataManager: kraft
+          metadataManager: KRaft
           authentication:
             - authenticationClass: kerberos-auth-$NAMESPACE
           tls:

diff --git a/tests/templates/kuttl/kraft-kerberos/70-scale-controller-down.yaml.j2 b/tests/templates/kuttl/kraft-kerberos/70-scale-controller-down.yaml.j2
@@ -21,7 +21,7 @@ commands:
           pullPolicy: IfNotPresent
         clusterConfig:
           # KRaft: metadata is managed by the controllers role, no ZooKeeper involved.
-          metadataManager: kraft
+          metadataManager: KRaft
           authentication:
             - authenticationClass: kerberos-auth-$NAMESPACE
           tls:

diff --git a/tests/templates/kuttl/operations-kraft/20-install-kafka.yaml.j2 b/tests/templates/kuttl/operations-kraft/20-install-kafka.yaml.j2
@@ -17,7 +17,7 @@ spec:
 {% endif %}
     pullPolicy: IfNotPresent
   clusterConfig:
-    metadataManager: kraft
+    metadataManager: KRaft
 {% if lookup('env', 'VECTOR_AGGREGATOR') %}
     vectorAggregatorConfigMapName: vector-aggregator-discovery
 {% endif %}

diff --git a/tests/templates/kuttl/operations-kraft/25-pause-kafka.yaml.j2 b/tests/templates/kuttl/operations-kraft/25-pause-kafka.yaml.j2
@@ -17,7 +17,7 @@ spec:
 {% endif %}
     pullPolicy: IfNotPresent
   clusterConfig:
-    metadataManager: kraft
+    metadataManager: KRaft
 {% if lookup('env', 'VECTOR_AGGREGATOR') %}
     vectorAggregatorConfigMapName: vector-aggregator-discovery
 {% endif %}

diff --git a/tests/templates/kuttl/operations-kraft/30-stop-kafka.yaml.j2 b/tests/templates/kuttl/operations-kraft/30-stop-kafka.yaml.j2
@@ -17,7 +17,7 @@ spec:
 {% endif %}
     pullPolicy: IfNotPresent
   clusterConfig:
-    metadataManager: kraft
+    metadataManager: KRaft
 {% if lookup('env', 'VECTOR_AGGREGATOR') %}
     vectorAggregatorConfigMapName: vector-aggregator-discovery
 {% endif %}

diff --git a/tests/templates/kuttl/operations-kraft/50-restart-kafka.yaml.j2 b/tests/templates/kuttl/operations-kraft/50-restart-kafka.yaml.j2
@@ -16,7 +16,7 @@ spec:
     productVersion: "{{ test_scenario['values']['kafka-kraft'] }}"
 {% endif %}
   clusterConfig:
-    metadataManager: kraft
+    metadataManager: KRaft
 {% if lookup('env', 'VECTOR_AGGREGATOR') %}
     vectorAggregatorConfigMapName: vector-aggregator-discovery
 {% endif %}

diff --git a/tests/templates/kuttl/operations-kraft/60-scale-controller-up.yaml.j2 b/tests/templates/kuttl/operations-kraft/60-scale-controller-up.yaml.j2
@@ -16,7 +16,7 @@ spec:
     productVersion: "{{ test_scenario['values']['kafka-kraft'] }}"
 {% endif %}
   clusterConfig:
-    metadataManager: kraft
+    metadataManager: KRaft
 {% if lookup('env', 'VECTOR_AGGREGATOR') %}
     vectorAggregatorConfigMapName: vector-aggregator-discovery
 {% endif %}

diff --git a/tests/templates/kuttl/operations-kraft/70-scale-controller-down.yaml.j2 b/tests/templates/kuttl/operations-kraft/70-scale-controller-down.yaml.j2
@@ -16,7 +16,7 @@ spec:
     productVersion: "{{ test_scenario['values']['kafka-kraft'] }}"
 {% endif %}
   clusterConfig:
-    metadataManager: kraft
+    metadataManager: KRaft
 {% if lookup('env', 'VECTOR_AGGREGATOR') %}
     vectorAggregatorConfigMapName: vector-aggregator-discovery
 {% endif %}

diff --git a/tests/templates/kuttl/operations-kraft/80-scale-broker-down.yaml.j2 b/tests/templates/kuttl/operations-kraft/80-scale-broker-down.yaml.j2
@@ -23,7 +23,7 @@ spec:
 {% endif %}
 {% if lookup('env', 'VECTOR_AGGREGATOR') %}
   clusterConfig:
-    metadataManager: kraft
+    metadataManager: KRaft
     vectorAggregatorConfigMapName: vector-aggregator-discovery
 {% endif %}
   controllers:

diff --git a/tests/templates/kuttl/operations-kraft/90-controller-shutdown.yaml.j2 b/tests/templates/kuttl/operations-kraft/90-controller-shutdown.yaml.j2
@@ -23,7 +23,7 @@ spec:
 {% endif %}
 {% if lookup('env', 'VECTOR_AGGREGATOR') %}
   clusterConfig:
-    metadataManager: kraft
+    metadataManager: KRaft
     vectorAggregatorConfigMapName: vector-aggregator-discovery
 {% endif %}
   controllers:

diff --git a/tests/templates/kuttl/smoke-kraft/30-install-kafka.yaml.j2 b/tests/templates/kuttl/smoke-kraft/30-install-kafka.yaml.j2
@@ -69,7 +69,7 @@ spec:
 {% endif %}
     pullPolicy: IfNotPresent
   clusterConfig:
-    metadataManager: kraft
+    metadataManager: KRaft
     authentication:
       - authenticationClass: test-kafka-client-auth-tls
     tls:

diff --git a/tests/templates/kuttl/upgrade/02-install-kafka.yaml.j2 b/tests/templates/kuttl/upgrade/02-install-kafka.yaml.j2
@@ -34,7 +34,7 @@ spec:
   clusterConfig:
     # Need to set this explicitly because the default would be zookeeper for 3.9.2
     # but we don't want to test zookeeper -> kraft migration here
-    metadataManager: kraft
+    metadataManager: KRaft
 {% if test_scenario['values']['use-client-auth-tls'] == 'true' %}
     authentication:
       - authenticationClass: test-kafka-client-auth-tls