diff --git a/.github/workflows/copilot-setup-steps.yml b/.github/workflows/copilot-setup-steps.yml
new file mode 100644
index 0000000..43c706c
--- /dev/null
+++ b/.github/workflows/copilot-setup-steps.yml
@@ -0,0 +1,42 @@
+name: "Copilot Setup Steps"
+
+# Automatically run the setup steps when they are changed to allow for easy validation, and
+# allow manual testing through the repository's "Actions" tab
+on:
+  workflow_dispatch:
+  push:
+    paths:
+      - .github/workflows/copilot-setup-steps.yml
+  pull_request:
+    paths:
+      - .github/workflows/copilot-setup-steps.yml
+
+jobs:
+  # The job MUST be called `copilot-setup-steps` or it will not be picked up by Copilot.
+  copilot-setup-steps:
+    runs-on: ubuntu-latest
+
+    # Set the permissions to the lowest permissions possible needed for your steps.
+    # Copilot will be given its own token for its operations.
+    permissions:
+      # If you want to clone the repository as part of your setup steps, for example to install dependencies, you'll need the `contents: read` permission.
+      # If you don't clone the repository in your setup steps, Copilot will do this for you automatically after the steps complete.
+      contents: read
+
+    # You can define any steps you want, and they will run before the agent starts.
+    # If you do not check out your code, Copilot will do this for you.
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Setup PHP 8.4
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: '8.4'
+          github-token: ${{ secrets.GH_PAT_TOKEN || github.token }}
+          tools: composer:v2
+          coverage: none
+          ini-values: memory_limit=-1
+
+      - name: Install Composer dependencies
+        run: composer install --no-interaction --no-progress --prefer-dist
diff --git a/CLAUDE.md b/CLAUDE.md
index 59fb408..49dfd50 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -8,6 +8,11 @@ Parser Reflection is a **deprecated** PHP library (deprecated in favor of [Bette
 
 Requires PHP >=8.4. Namespace: `Go\ParserReflection\`.
 
+## Agent runtime requirement
+
+- Agents must run on PHP **8.4 or higher**.
+- If the runtime is PHP **8.3.x**, agents should not attempt dependency installation or test validation and should report that PHP **8.4+** is required.
+
 ## Commands
 
 ```bash