diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index be06c75..73c23d3 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -15,7 +15,7 @@ jobs:
       - uses: actions/setup-java@be666c2fcd27ec809703dec50e508c2fdc7f6654 # v5
         with:
           distribution: temurin
-          java-version: 21
+          java-version: 25
 
       - uses: gradle/actions/setup-gradle@f29f5a9d7b09a7c6b29859002d29d24e1674c884 # v5
 
diff --git a/CLAUDE.md b/CLAUDE.md
index e6fac4a..47e1a44 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -9,7 +9,7 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 ./gradlew check      # Lint (ktlint) + test (Spek2)
 ```
 
-JDK 21+ required. Tests use snapshot testing (snapshots in `src/test/resources/__snapshot__/`).
+JDK 25+ required. Tests use snapshot testing (snapshots in `src/test/resources/__snapshot__/`).
 
 ## Architecture
 
diff --git a/build.gradle.kts b/build.gradle.kts
index 457e316..0607dd2 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -36,7 +36,7 @@ dependencies {
 }
 
 kotlin {
-  jvmToolchain(21)
+  jvmToolchain(25)
 }
 
 application {
diff --git a/renovate.json b/renovate.json
index fc4c748..fae8139 100644
--- a/renovate.json
+++ b/renovate.json
@@ -1,5 +1,29 @@
 {
   "extends": ["github>henrist/renovate-config:default"],
   "automerge": true,
-  "automergeType": "branch"
+  "automergeType": "branch",
+  "customManagers": [
+    {
+      "customType": "regex",
+      "fileMatch": ["build\\.gradle\\.kts$"],
+      "matchStrings": ["jvmToolchain\\((?<currentValue>\\d+)\\)"],
+      "depNameTemplate": "java",
+      "datasourceTemplate": "java-version",
+      "extractVersionTemplate": "^(?<version>\\d+)"
+    },
+    {
+      "customType": "regex",
+      "fileMatch": ["^\\.github/workflows/[^/]+\\.yml$"],
+      "matchStrings": ["java-version:\\s*(?<currentValue>\\d+)"],
+      "depNameTemplate": "java",
+      "datasourceTemplate": "java-version",
+      "extractVersionTemplate": "^(?<version>\\d+)"
+    }
+  ],
+  "packageRules": [
+    {
+      "groupName": "jdk",
+      "matchPackageNames": ["eclipse-temurin", "java"]
+    }
+  ]
 }