diff --git a/.github/renovate.json b/.github/renovate.json5
similarity index 100%
rename from .github/renovate.json
rename to .github/renovate.json5
diff --git a/.github/workflows/renovate-config-validator.yaml b/.github/workflows/renovate-config-validator.yaml
index e4b1c72..ee419e2 100644
--- a/.github/workflows/renovate-config-validator.yaml
+++ b/.github/workflows/renovate-config-validator.yaml
@@ -1,28 +1,41 @@
-name: Validate Renovate Config
+name: "Validate Renovate Config"
 
 on:
-  push
+  push:
 
 jobs:
   config:
     strategy:
+      fail-fast: false
       matrix:
         include:
 
-          - name: Own Config
-            config-files: .github/renovate.json
+          - name: "Own Config"
+            config-files: .github/renovate.json5
 
-          - name: Shared Config
-            config-files: default.json # group.json is not possible yet
+          - name: "Shared Config"
+            config-files: default.json
 
-    name: 🔍 ${{ matrix.name }}
+          - name: "Shared Config (Actual)"
+            config-files: default.json5
+
+          # Not possible yet: "Configuration Error: Invalid configuration option: all".
+          #- name: "Group Presets"
+          #  config-files: group.json5
+
+    name: "🔍 ${{ matrix.name }}"
+    timeout-minutes: 2
+    permissions:
+      # actions/checkout
+      contents: read
     runs-on: ubuntu-latest
     steps:
 
-      - name: Checkout ${{ github.ref }} branch in ${{ github.repository }} repository.
+      - name: "Checkout ${{ github.ref }} branch in ${{ github.repository }} repository."
         uses: actions/checkout@v4
 
-      - name: Run renovate-config-validator on shared config.
+      - name: "Run renovate-config-validator on shared config."
+        shell: bash
         run: >
           npx
           --yes
diff --git a/README.md b/README.md
index 48afd9d..cf93f28 100644
--- a/README.md
+++ b/README.md
@@ -2,15 +2,16 @@
 Configuration files for renovatebot installed in [repositories](https://github.com/TWiStErRob?tab=repositories).
 
 ## Naming
-Note: this repository is called `renovate-config` so it'll be [picked up automatically by Renovate](https://docs.renovatebot.com/config-presets/#organization-level-presets).
+ * This repository is called `renovate-config` so it'll be [picked up automatically by Renovate](https://docs.renovatebot.com/config-presets/#organization-level-presets).
+ * The shared config preset is called `default.json` as that's the [only supported name](https://docs.renovatebot.com/config-presets/).
+ * `default.json5` is the actual preset referenced from `default.json`, so that I can use JSON5 features.
 
 # Installation
  1. Add repository to [Renovate GitHub app installation](https://github.com/settings/installations/24636554).
  2. Wait for "Configure Renovate" onboarding PR.
  3. It should automatically pick up [local>TWiStErRob/renovate-config](default.json)
- 4. Move `/renovate.json` to `/.github/renovate.json`.
- 5. Commit and push to `renovate/configure` branch.
- 6. Review, configure as necessary and merge PR.
+ 4. Commit and push to `renovate/configure` branch.
+ 5. Review, configure as necessary and merge PR.
 
 # Development
 IntelliJ IDEA has json-schema validation and auto-complete support, so it the recommended editor.
diff --git a/config.js b/config.js
index f9a0139..4cdd021 100644
--- a/config.js
+++ b/config.js
@@ -1,5 +1,6 @@
 const fs = require('fs');
-const configFilePath = "P:\\projects\\workspace\\net.twisterrob.gradle\\.github\\renovate.json";
+const JSON5 = require('json5');
+const configFilePath = "P:\\projects\\contrib\\github-twisterrob-renovate\\.github\\renovate.json5";
 const configFileText = fs.readFileSync(configFilePath, "utf8");
 module.exports = {
 	// https://docs.renovatebot.com/self-hosted-configuration/#dryrun
@@ -27,7 +28,7 @@ module.exports = {
 	// Command line: last parameter in form of user/repo
 	// https://docs.renovatebot.com/self-hosted-configuration/#repositories
 	"repositories": [
-		{"repository": "TWiStErRob/net.twisterrob.gradle"},
+		{ "repository": "TWiStErRob/renovate-config" },
 	],
 
 	// Reduce noise:
@@ -54,6 +55,6 @@ module.exports = {
 	// rather than from the loaded JSON. REPORT this sounds like a bug.
 	"force": {
 		// This loads a local file instead.
-		...JSON.parse(configFileText)
-	}
+		...JSON5.parse(configFileText),
+	},
 };
diff --git a/default.json b/default.json
index 1e53c08..640da8a 100644
--- a/default.json
+++ b/default.json
@@ -1,65 +1,6 @@
 {
 	"$schema": "https://docs.renovatebot.com/renovate-schema.json",
-	"onboardingConfigFileName": ".github/renovate.json",
 	"extends": [
-		"config:recommended",
-		":disableRateLimiting",
-		"github>TWiStErRob/renovate-config:group/all"
-	],
-	"semanticCommits": "disabled",
-	"configMigration": true,
-	"commitMessageExtra": "from {{{currentValue}}} to {{{newValue}}}{{#if isMajor}} (major v{{{newMajor}}}){{else}}{{/if}}",
-	"labels": ["in:dependencies"],
-	"separateMajorMinor": true,
-	"separateMultipleMajor": true,
-	"separateMinorPatch": true,
-	"minimumReleaseAge": "8 hours",
-	"internalChecksFilter": "strict",
-	"ignorePaths": [
-		"do-not-ignore-anything"
-	],
-	"packageRules": [
-		{
-			"description": "Auto-merge all small changes, except for unstable versions.",
-			"matchUpdateTypes": ["minor", "patch"],
-			"matchCurrentVersion": "!/^0/",
-			"automerge": true
-		},
-		{
-			"description": "Auto-merge all updates of specific dependencies, their 0.x versions are stable and well-controlled.",
-			"matchUpdateTypes": ["minor", "patch"],
-			"matchCurrentVersion": "/^0/",
-			"matchPackageNames": [
-				"org.gradle.toolchains.foojay-resolver-convention"
-			],
-			"automerge": true
-		},
-		{
-			"description": "Auto-merge all digest updates, TODO why?",
-			"matchUpdateTypes": ["digest"],
-			"automerge": true
-		},
-		{
-			"description": "Wait for npm dependencies, they often have small patch releases in quick succession.",
-			"matchDatasources": ["npm"],
-			"minimumReleaseAge": "3 days"
-		},
-		{
-			"description": "Merge my packages as soon as possible.",
-			"matchPackagePrefixes": ["net.twisterrob"],
-			"minimumReleaseAge": "0 minutes"
-		},
-		{
-			"description": "Pin my reusable workflows, semver might not be true.",
-			"matchDepTypes": ["action"],
-			"matchPackageNames": [
-				"TWiStErRob/github-workflows"
-			],
-			"pinDigests": true
-		}
-	],
-	"gradle-wrapper": {
-		"description": "Update Gradle wrapper to non-stable versions",
-		"ignoreUnstable": false
-	}
+		"local>TWiStErRob/renovate-config:default.json5"
+	]
 }
diff --git a/default.json5 b/default.json5
new file mode 100644
index 0000000..55c3430
--- /dev/null
+++ b/default.json5
@@ -0,0 +1,65 @@
+{
+	"$schema": "https://docs.renovatebot.com/renovate-schema.json",
+	"onboardingConfigFileName": ".github/renovate.json5",
+	"extends": [
+		"config:recommended",
+		":disableRateLimiting",
+		"local>TWiStErRob/renovate-config:group.json5/all"
+	],
+	"semanticCommits": "disabled",
+	"configMigration": true,
+	"commitMessageExtra": "from {{{currentValue}}} to {{{newValue}}}{{#if isMajor}} (major v{{{newMajor}}}){{else}}{{/if}}",
+	"labels": ["in:dependencies"],
+	"separateMajorMinor": true,
+	"separateMultipleMajor": true,
+	"separateMinorPatch": true,
+	"minimumReleaseAge": "8 hours",
+	"internalChecksFilter": "strict",
+	"ignorePaths": [
+		"do-not-ignore-anything"
+	],
+	"packageRules": [
+		{
+			"description": "Auto-merge all small changes, except for unstable versions.",
+			"matchUpdateTypes": ["minor", "patch"],
+			"matchCurrentVersion": "!/^0/",
+			"automerge": true
+		},
+		{
+			"description": "Auto-merge all updates of specific dependencies, their 0.x versions are stable and well-controlled.",
+			"matchUpdateTypes": ["minor", "patch"],
+			"matchCurrentVersion": "/^0/",
+			"matchPackageNames": [
+				"org.gradle.toolchains.foojay-resolver-convention"
+			],
+			"automerge": true
+		},
+		{
+			"description": "Auto-merge all digest updates, TODO why?",
+			"matchUpdateTypes": ["digest"],
+			"automerge": true
+		},
+		{
+			"description": "Wait for npm dependencies, they often have small patch releases in quick succession.",
+			"matchDatasources": ["npm"],
+			"minimumReleaseAge": "3 days"
+		},
+		{
+			"description": "Merge my packages as soon as possible.",
+			"matchPackagePrefixes": ["net.twisterrob"],
+			"minimumReleaseAge": "0 minutes"
+		},
+		{
+			"description": "Pin my reusable workflows, semver might not be true.",
+			"matchDepTypes": ["action"],
+			"matchPackageNames": [
+				"TWiStErRob/github-workflows"
+			],
+			"pinDigests": true
+		}
+	],
+	"gradle-wrapper": {
+		"description": "Update Gradle wrapper to non-stable versions",
+		"ignoreUnstable": false
+	}
+}
diff --git a/group.json b/group.json5
similarity index 90%
rename from group.json
rename to group.json5
index d1d65d0..06adb41 100644
--- a/group.json
+++ b/group.json5
@@ -4,21 +4,21 @@
 		"extends": [
 			"group:monorepos",
 			"group:recommended",
-			"github>TWiStErRob/renovate-config:group/twisterrob-gradle",
-			"github>TWiStErRob/renovate-config:group/github-artifacts",
-			"github>TWiStErRob/renovate-config:group/github-pages",
-			"github>TWiStErRob/renovate-config:group/kotlin",
-			"github>TWiStErRob/renovate-config:group/ktor",
-			"github>TWiStErRob/renovate-config:group/detekt",
-			"github>TWiStErRob/renovate-config:group/agp",
-			"github>TWiStErRob/renovate-config:group/agp-lint",
-			"github>TWiStErRob/renovate-config:group/androidx",
-			"github>TWiStErRob/renovate-config:group/androidx-test",
-			"github>TWiStErRob/renovate-config:group/mockito",
-			"github>TWiStErRob/renovate-config:group/neo4j",
-			"github>TWiStErRob/renovate-config:group/log4j2",
-			"github>TWiStErRob/renovate-config:group/jackson",
-			"github>TWiStErRob/renovate-config:group/notion"
+			"local>TWiStErRob/renovate-config:group.json5/twisterrob-gradle",
+			"local>TWiStErRob/renovate-config:group.json5/github-artifacts",
+			"local>TWiStErRob/renovate-config:group.json5/github-pages",
+			"local>TWiStErRob/renovate-config:group.json5/kotlin",
+			"local>TWiStErRob/renovate-config:group.json5/ktor",
+			"local>TWiStErRob/renovate-config:group.json5/detekt",
+			"local>TWiStErRob/renovate-config:group.json5/agp",
+			"local>TWiStErRob/renovate-config:group.json5/agp-lint",
+			"local>TWiStErRob/renovate-config:group.json5/androidx",
+			"local>TWiStErRob/renovate-config:group.json5/androidx-test",
+			"local>TWiStErRob/renovate-config:group.json5/mockito",
+			"local>TWiStErRob/renovate-config:group.json5/neo4j",
+			"local>TWiStErRob/renovate-config:group.json5/log4j2",
+			"local>TWiStErRob/renovate-config:group.json5/jackson",
+			"local>TWiStErRob/renovate-config:group.json5/notion"
 		]
 	},
 	"twisterrob-gradle": {
diff --git a/package.json b/package.json
index 043838f..239f8d7 100644
--- a/package.json
+++ b/package.json
@@ -4,6 +4,7 @@
 		"renovate": "renovate"
 	},
 	"devDependencies": {
+		"json5": "2.2.3",
 		"renovate": "37.0.0"
 	},
 	"jshintConfig": {