diff --git a/.github/actions/changed_files/action.yml b/.github/actions/changed_files/action.yml
index f2fc336b3..d491a2d23 100644
--- a/.github/actions/changed_files/action.yml
+++ b/.github/actions/changed_files/action.yml
@@ -19,10 +19,12 @@ runs:
   # https://docs.github.com/en/actions/creating-actions/creating-a-composite-action
   using: "composite"
   steps:
-    - name: "Checkout PR branch (with test merge-commit)"
-      uses: actions/checkout@v4
-      with:
-        fetch-depth: 2 # to also fetch parent of PR
+    # This has to be done in the main workflow, not in the action, because
+    # otherwise this reusable action is not available in the workflow.
+    # - name: "Checkout PR branch (with test merge-commit)"
+    #   uses: actions/checkout@v4
+    #   with:
+    #     fetch-depth: 2 # to also fetch parent of PR
 
     # Adapted from this great comment [1]. Git diff adapted from [2].
     # "|| test $? = 1;" is used to ignore the exit code of grep when no files
@@ -37,6 +39,6 @@ runs:
       shell: bash
       id: get-changed-files
       run: |
-        files_pretty=$(git diff --name-only --diff-filter=ACMR -r HEAD^1...HEAD | grep '${{inputs.file-extensions}}' || test $? = 1;)
+        files_pretty=$(git diff --name-only --diff-filter=ACMR -r HEAD^1...HEAD | grep -e '${{inputs.file-extensions}}' || test $? = 1;)
         printf "🎴 Changed files: \n$files_pretty"
-        echo "files=$(echo ${files_pretty} | xargs)" >> $GITHUB_ENV
+        echo "files=$(echo ${files_pretty} | xargs)" >> $GITHUB_OUTPUT
diff --git a/.github/workflows/linter.yml b/.github/workflows/linter.yml
index 5145bd761..a627376f4 100644
--- a/.github/workflows/linter.yml
+++ b/.github/workflows/linter.yml
@@ -21,29 +21,26 @@ jobs:
         uses: actions/checkout@v4
         with:
           fetch-depth: 2 # to also fetch parent of PR
-      
-      # Adapted from this great comment [1]. Git diff adapted from [2].
-      # "|| test $? = 1;" is used to ignore the exit code of grep when no files
-      # are found matching the pattern. For the "three dots" ... syntax, see [3].
+
       - name: Get changed files
-        run: |
-          files=$(git diff --name-only --diff-filter=ACMR -r HEAD^1...HEAD | grep '\.rb$' || test $? = 1;)
-          printf "🎴 Changed ruby files: \n$files"
-          echo "CHANGED_FILES=$(echo ${files} | xargs)" >> $GITHUB_ENV
-      
+        id: rb-changed
+        uses: ./.github/actions/changed_files/
+        with:
+          file-extensions: \.rb$
+
       - name: Set up Ruby 3
-        if: env.CHANGED_FILES != ''
+        if: ${{ steps.rb-changed.outputs.changed-files != ''}}
         uses: ruby/setup-ruby@v1
         with:
           ruby-version: 3.1.4
           bundler-cache: true
 
       - name: Run RuboCop
-        if: env.CHANGED_FILES != ''
+        if: ${{ steps.rb-changed.outputs.changed-files != ''}}
         run: |
           echo "🚨 Running RuboCop version: $(bundle info rubocop | head -1)"
           bundle exec rubocop --format github --fail-level 'convention' --force-exclusion -- $CHANGED_FILES
-  
+
   eslint:
       name: ESLint (JS)
       runs-on: ubuntu-latest
@@ -53,22 +50,28 @@ jobs:
           with:
             fetch-depth: 2 # to also fetch parent of PR
 
-        - name: Checkout code & get changed files
+        - name: Get changed files
           id: eslint-changed
           uses: ./.github/actions/changed_files/
           with:
             file-extensions: \.js$|\.js.erb$
 
+        - name: Trial and error
+          if: ${{ steps.eslint-changed.outputs.changed-files != ''}}
+          run: 'echo "Changed files: aa${{ steps.eslint-changed.outputs.changed-files }}bb"'
+
         - name: Setup Node.js
-          if: ${{ steps.eslint-changed.outputs.changed-files }} != ''
+          if: ${{ steps.eslint-changed.outputs.changed-files != ''}}
           uses: actions/setup-node@v4
           with:
             node-version: '20' # End of Life (EOL): April 2026
         
         - name: Install dependencies
-          if: ${{ steps.eslint-changed.outputs.changed-files }} != ''
+          if: ${{ steps.eslint-changed.outputs.changed-files != ''}}
           run: yarn install
 
         - name: Run ESLint
-          if: ${{ steps.eslint-changed.outputs.changed-files }} != ''
-          run: yarn run eslint --ignore-path .gitignore --max-warnings 0 ${{ steps.eslint-changed.outputs.changed-files }}
+          if: ${{ steps.eslint-changed.outputs.changed-files != ''}}
+          run: |
+            echo "🚨 Running ESLint version: $(yarn run eslint --version)"
+            yarn run eslint --ignore-path .gitignore --max-warnings 0 ${{ steps.eslint-changed.outputs.changed-files }}