diff --git a/.github/workflows/pulsar-ci-flaky.yaml b/.github/workflows/pulsar-ci-flaky.yaml
index dd58a31b4780c..105fa508b49fb 100644
--- a/.github/workflows/pulsar-ci-flaky.yaml
+++ b/.github/workflows/pulsar-ci-flaky.yaml
@@ -25,9 +25,9 @@ on:
       - branch-*
       - pulsar-*
   schedule:
-    # scheduled job with JDK 21
-    - cron: '0 12 * * *'
     # scheduled job with JDK 25
+    - cron: '0 12 * * *'
+    # scheduled job with JDK 21
     # if cron expression is changed, make sure to update the expression in jdk_major_version step in preconditions job
     - cron: '0 6 * * *'
   workflow_dispatch:
@@ -42,9 +42,9 @@ on:
         required: true
         type: choice
         options:
-          - '21'
           - '25'
-        default: '21'
+          - '21'
+        default: '25'
       trace_test_resource_cleanup:
         description: 'Collect thread & heap information before exiting a test JVM. When set to "on", thread dump and heap histogram will be collected. When set to "full", a heap dump will also be collected.'
         required: true
@@ -104,13 +104,13 @@ jobs:
       - name: Select JDK major version
         id: jdk_major_version
         run: |
-          # use JDK 25 for the scheduled build with cron expression '0 6 * * *'
+          # use JDK 21 for the scheduled build with cron expression '0 6 * * *'
           if [[ "${{ github.event_name == 'schedule' && github.event.schedule == '0 6 * * *' && 'true' || 'false' }}" == "true" ]]; then
-            echo "jdk_major_version=25" >> $GITHUB_OUTPUT
+            echo "jdk_major_version=21" >> $GITHUB_OUTPUT
             exit 0
           fi
-          # use JDK 21 for build unless overridden with workflow_dispatch input
-          echo "jdk_major_version=${{ github.event_name == 'workflow_dispatch' && github.event.inputs.jdk_major_version || '21'}}" >> $GITHUB_OUTPUT
+          # use JDK 25 for build unless overridden with workflow_dispatch input
+          echo "jdk_major_version=${{ github.event_name == 'workflow_dispatch' && github.event.inputs.jdk_major_version || '25'}}" >> $GITHUB_OUTPUT
 
       - name: checkout
         if: ${{ github.event_name == 'pull_request' }}
diff --git a/.github/workflows/pulsar-ci.yaml b/.github/workflows/pulsar-ci.yaml
index 3a7a94f0559b1..50d2240ac7ac1 100644
--- a/.github/workflows/pulsar-ci.yaml
+++ b/.github/workflows/pulsar-ci.yaml
@@ -25,9 +25,9 @@ on:
       - branch-*
       - pulsar-*
   schedule:
-    # scheduled job with JDK 21
-    - cron: '0 12 * * *'
     # scheduled job with JDK 25
+    - cron: '0 12 * * *'
+    # scheduled job with JDK 21
     # if cron expression is changed, make sure to update the expression in jdk_major_version step in preconditions job
     - cron: '0 6 * * *'
   workflow_dispatch:
@@ -37,9 +37,9 @@ on:
         required: true
         type: choice
         options:
-          - '21'
           - '25'
-        default: '21'
+          - '21'
+        default: '25'
       trace_test_resource_cleanup:
         description: 'Collect thread & heap information before exiting a test JVM. When set to "on", thread dump and heap histogram will be collected. When set to "full", a heap dump will also be collected.'
         required: true
@@ -97,13 +97,13 @@ jobs:
       - name: Select JDK major version
         id: jdk_major_version
         run: |
-          # use JDK 25 for the scheduled build with cron expression '0 6 * * *'
+          # use JDK 21 for the scheduled build with cron expression '0 6 * * *'
           if [[ "${{ github.event_name == 'schedule' && github.event.schedule == '0 6 * * *' && 'true' || 'false' }}" == "true" ]]; then
-            echo "jdk_major_version=25" >> $GITHUB_OUTPUT
+            echo "jdk_major_version=21" >> $GITHUB_OUTPUT
             exit 0
           fi
-          # use JDK 21 for build unless overridden with workflow_dispatch input
-          echo "jdk_major_version=${{ github.event_name == 'workflow_dispatch' && github.event.inputs.jdk_major_version || '21'}}" >> $GITHUB_OUTPUT
+          # use JDK 25 for build unless overridden with workflow_dispatch input
+          echo "jdk_major_version=${{ github.event_name == 'workflow_dispatch' && github.event.inputs.jdk_major_version || '25'}}" >> $GITHUB_OUTPUT
 
       - name: checkout
         if: ${{ github.event_name == 'pull_request' }}
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index 03ffee71dd94a..0635d1c2c2492 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -18,7 +18,7 @@
 #
 [versions]
 # Docker
-docker-jdk = "21"
+docker-jdk = "25"
 pulsar-client-python = "3.12.0"
 # Code quality
 checkstyle = "13.3.0"