diff --git a/.devcontainer/Dockerfile b/.devcontainer/Dockerfile
new file mode 100644
index 0000000000000..3e71214f8c8db
--- /dev/null
+++ b/.devcontainer/Dockerfile
@@ -0,0 +1,70 @@
+# Start from the official PHP 8.2 image with Apache
+FROM php:8.2-apache-bookworm
+
+# Install system dependencies, Node.js, Composer, and Cypress dependencies
+RUN apt-get update && apt-get install -y \
+    # System tools and git
+    git \
+    unzip \
+    curl \
+    sudo \
+    # PHP extensions dependencies
+    libpng-dev \
+    libonig-dev \
+    libxml2-dev \
+    libzip-dev \
+    # MySQL client AND server
+    default-mysql-client \
+    default-mysql-server \
+    # Cypress dependencies
+    xvfb \
+    libgtk2.0-0 \
+    libgtk-3-0 \
+    libgbm-dev \
+    libnotify-dev \
+    libnss3 \
+    libxss1 \
+    libasound2 \
+    libxtst6 \
+    xauth \
+    libldap2-dev \
+    libgd-dev \
+    && \
+    # Install the required PHP extensions for Zip and MySQL
+    docker-php-ext-install zip mysqli gd ldap && \
+    # Install Node.js (LTS version)
+    curl -fsSL https://deb.nodesource.com/setup_lts.x | bash - && \
+    apt-get install -y nodejs && \
+    # Install Composer globally
+    curl -sS https://getcomposer.org/installer | php -- --install-dir=/usr/local/bin --filename=composer && \
+    # Install Xdebug
+    pecl install xdebug && \
+    # Clean up apt cache to reduce image size
+    apt-get clean && rm -rf /var/lib/apt/lists/*
+
+# After installing everything
+RUN sed -i 's|/var/www/html|/workspaces/joomla-cms|g' /etc/apache2/sites-available/000-default.conf \
+    && sed -i 's|/var/www/html|/workspaces/joomla-cms|g' /etc/apache2/apache2.conf
+
+# Enable Apache's rewrite module and set the ServerName to prevent warnings
+RUN a2enmod rewrite \
+    && echo "ServerName localhost" >> /etc/apache2/apache2.conf
+    
+RUN apt-get update && apt-get install -y ssl-cert && \
+    a2enmod ssl && \
+    a2ensite 000-default && \
+    a2ensite default-ssl && \
+    sed -i 's|/var/www/html|/workspaces/joomla-cms|g' /etc/apache2/sites-available/default-ssl.conf && \
+    echo '<Directory /workspaces/joomla-cms>\n    Options Indexes FollowSymLinks\n    AllowOverride All\n    Require all granted\n</Directory>' >> /etc/apache2/sites-available/default-ssl.conf
+
+# Create a custom PHP configuration file to enable file uploads and a log directory
+RUN mkdir -p /var/log/ && \
+    touch /var/log/php_errors.log && \
+    chown -R www-data:www-data /var/log/ && \
+    chmod 766 /var/log/php_errors.log && \
+    echo "upload_tmp_dir = /tmp" > /usr/local/etc/php/conf.d/custom-php.ini && \
+    echo "post_max_size = 64M" >> /usr/local/etc/php/conf.d/custom-php.ini && \
+    echo "upload_max_filesize = 64M" >> /usr/local/etc/php/conf.d/custom-php.ini && \
+    echo "log_errors = On" >> /usr/local/etc/php/conf.d/custom-php.ini && \
+    echo "error_log = /var/log/php_errors.log" >> /usr/local/etc/php/conf.d/custom-php.ini && \
+    echo "error_reporting = E_ALL" >> /usr/local/etc/php/conf.d/custom-php.ini
diff --git a/.devcontainer/devcontainer.json b/.devcontainer/devcontainer.json
new file mode 100644
index 0000000000000..9a93f372e6177
--- /dev/null
+++ b/.devcontainer/devcontainer.json
@@ -0,0 +1,44 @@
+{
+    "name": "Joomla Dev Environment",
+    "dockerComposeFile": "docker-compose.yml",
+    "service": "app",
+    "workspaceFolder": "/workspaces/joomla-cms",
+    "features": {
+        "ghcr.io/devcontainers/features/desktop-lite:1": {}
+    },
+    "portsAttributes": {
+        "443" : {
+            "label": "Web Server (Joomla & phpmyadmin)",
+            "onAutoForward": "silent"
+        },
+        "6080": {
+            "label": "Cypress GUI",
+            "onAutoForward": "silent"
+        }
+    },
+    "postCreateCommand": "bash ./.devcontainer/post-create.sh",
+    "customizations": {
+        "vscode": {
+            "extensions": [
+                "xdebug.php-debug",
+                "bmewburn.vscode-intelephense-client",
+                "esbenp.prettier-vscode"
+            ],
+            "settings": {
+                "launch": {
+                    "version": "0.2.0",
+                    "configurations": [
+                        {
+                            "name": "Listen for Xdebug",
+                            "type": "php",
+                            "request": "launch",
+                            "port": 9003,
+                            "log": false
+                        }
+                    ]
+                }
+            }
+        }
+    },
+    "remoteUser": "root"
+}
diff --git a/.devcontainer/docker-compose.yml b/.devcontainer/docker-compose.yml
new file mode 100644
index 0000000000000..0d47fdd66174a
--- /dev/null
+++ b/.devcontainer/docker-compose.yml
@@ -0,0 +1,29 @@
+services:
+  app:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    volumes:
+      - ..:/workspaces/joomla-cms:cached
+      - ./xdebug.ini:/usr/local/etc/php/conf.d/99-xdebug.ini
+    ports:
+      - "80:80"
+      - "443:443"
+      - "3306:3306"
+      - "6080:6080"
+    command: sleep infinity
+
+  mysql:
+    image: mysql:8.0
+    command: --default-authentication-plugin=mysql_native_password
+    restart: unless-stopped
+    environment:
+      MYSQL_ROOT_PASSWORD: root
+      MYSQL_DATABASE: test_joomla
+      MYSQL_USER: joomla_ut
+      MYSQL_PASSWORD: joomla_ut
+    volumes:
+      - "mysql-data:/var/lib/mysql"
+
+volumes:
+  mysql-data:
diff --git a/.devcontainer/post-create.sh b/.devcontainer/post-create.sh
new file mode 100644
index 0000000000000..804916075b835
--- /dev/null
+++ b/.devcontainer/post-create.sh
@@ -0,0 +1,158 @@
+#!/bin/bash
+
+# Exit immediately if a command exits with a non-zero status.
+set -e
+
+echo "--- Starting Joomla Core Post-Creation Setup ---"
+
+# Configuration variables
+DB_NAME="test_joomla"
+DB_USER="joomla_ut"
+DB_PASS="joomla_ut"
+ADMIN_USER="ci-admin"
+ADMIN_REAL_NAME="jane doe"
+ADMIN_PASS="joomla-17082005"
+ADMIN_EMAIL="admin@example.com"
+JOOMLA_ROOT="/workspaces/joomla-cms"
+
+# Allow git commands to run safely in the container
+git config --global --add safe.directory $JOOMLA_ROOT
+
+# --- 1. Wait for MariaDB Service ---
+echo "--> Waiting for MariaDB to become available..."
+while ! mysqladmin ping -h"mysql" --silent; do
+    sleep 1
+done
+echo "✅ MariaDB is ready."
+
+# --- 2. Install Core Dependencies ---
+echo "--> Installing Composer and NPM dependencies..."
+composer install
+npm install
+echo "✅ Dependencies installed."
+
+# --- 3. Install Joomla from Repository Source ---
+echo "--> Installing Joomla using the local repository source..."
+rm -f configuration.php
+php installation/joomla.php install \
+    --site-name="Joomla CMS Test" \
+    --admin-user="$ADMIN_REAL_NAME" \
+    --admin-username="$ADMIN_USER" \
+    --admin-password="$ADMIN_PASS" \
+    --admin-email="$ADMIN_EMAIL" \
+    --db-type="mysqli" \
+    --db-host="mysql" \
+    --db-name="$DB_NAME" \
+    --db-user="$DB_USER" \
+    --db-pass="$DB_PASS" \
+    --db-prefix="jos_" \
+    --db-encryption="0" \
+    --public-folder=""
+echo "✅ Joomla installed."
+
+# --- 4. Configure Joomla for Development ---
+echo "--> Applying development settings..."
+# Enable debug mode and maximum error reporting for easier troubleshooting.
+php cli/joomla.php config:set error_reporting=maximum
+echo "✅ Development settings applied."
+
+# --- 5. Install and Configure phpMyAdmin ---
+PMA_ROOT="${JOOMLA_ROOT}/phpmyadmin"
+echo "--> Downloading phpMyAdmin into $PMA_ROOT..."
+PMA_VERSION=5.2.2
+mkdir -p $PMA_ROOT
+curl -o /tmp/phpmyadmin.tar.gz https://files.phpmyadmin.net/phpMyAdmin/${PMA_VERSION}/phpMyAdmin-${PMA_VERSION}-all-languages.tar.gz
+tar xf /tmp/phpmyadmin.tar.gz --strip-components=1 -C $PMA_ROOT
+rm /tmp/phpmyadmin.tar.gz
+cp $PMA_ROOT/config.sample.inc.php $PMA_ROOT/config.inc.php
+sed -i "/\['AllowNoPassword'\] = false/a \$cfg['Servers'][\$i]['host'] = 'mysql';" $PMA_ROOT/config.inc.php
+
+# --- 6. Apply Codespaces Host Fix ---
+# This ensures Joomla generates correct URLs when accessed through the forwarded port.
+echo "--> Applying Codespaces URL fix..."
+cat > "${JOOMLA_ROOT}/fix.php" << 'EOF'
+<?php
+// Fix for incorrect host when running behind the Codespaces reverse proxy.
+if (isset($_SERVER['HTTP_HOST']) && str_contains($_SERVER['HTTP_HOST'], 'localhost')) {
+    if (isset($_SERVER['HTTP_X_FORWARDED_HOST'])) {
+        $_SERVER['HTTP_HOST'] = $_SERVER['HTTP_X_FORWARDED_HOST'];
+        $_SERVER['SERVER_NAME'] = $_SERVER['HTTP_X_FORWARDED_HOST'];
+    }
+}
+EOF
+
+# Include fix in both entry points
+sed -i '2i require_once __DIR__ . "/fix.php";' $JOOMLA_ROOT/index.php
+sed -i '2i require_once __DIR__ . "/../fix.php";' $JOOMLA_ROOT/administrator/index.php
+
+echo "--> Ignoring local changes..."
+# For TRACKED files, tell Git to stop watching them for changes
+git update-index --assume-unchanged "index.php"
+git update-index --assume-unchanged "administrator/index.php"
+git update-index --assume-unchanged "package-lock.json"
+git update-index --assume-unchanged "tests/System/integration/install/Installation.cy.js"
+git update-index --assume-unchanged "tests/System/support/commands/config.mjs"
+
+# For NEW UNTRACKED files, add them to the local exclude file
+echo "cypress.config.js" >> ".git/info/exclude"
+echo "fix.php" >> ".git/info/exclude"
+echo "phpmyadmin" >> ".git/info/exclude"
+echo "codespace-details.txt" >> ".git/info/exclude"
+
+# --- 7. Finalize Permissions and Testing Tools ---
+echo "--> Setting up file permissions and Cypress..."
+sed -i \
+  -e "/\/\/ If exists, delete PHP configuration file to force a new installation/d" \
+  -e "/cy.task('deleteRelativePath', 'configuration.php');/d" \
+  -e "/cy.installJoomla(config);/d" \
+  tests/System/integration/install/Installation.cy.js
+sed -i "s/return cy.task('writeRelativeFile', { path: 'configuration.php', content });/return cy.task('writeRelativeFile', { path: 'configuration.php', content, mode: 0o775 });/" tests/System/support/commands/config.mjs
+
+# Ensure Cypress is executable and owned by the web server user
+chmod +x ./node_modules/.bin/cypress
+cp cypress.config.dist.mjs cypress.config.js
+npx cypress install
+sed -i -e "s|baseUrl:.*|baseUrl: 'https://localhost',|" -e "s/db_host: 'localhost'/db_host: 'mysql'/g" -e "s/db_user: 'root'/db_user: 'joomla_ut'/g" -e "s/db_password: ''/db_password: 'joomla_ut'/g" cypress.config.js
+
+# Restart Apache to apply all changes
+echo '<Directory /workspaces/joomla-cms>
+    AllowOverride All
+    Require all granted
+</Directory>' | sudo tee -a /etc/apache2/apache2.conf
+service apache2 restart
+
+# Set the group to www-data and enforce group permissions
+echo "--> Applying final group ownership and permissions..."
+chgrp -R www-data $JOOMLA_ROOT
+chmod -R g+rws $JOOMLA_ROOT
+
+echo "✅ Environment finalized."
+
+# --- 8. Display Setup Details ---
+# Save the details to a file for easy reference.
+DETAILS_FILE="${JOOMLA_ROOT}/codespace-details.txt"
+{
+    echo ""
+    echo "---"
+    echo "🚀 Joomla Core development environment is ready! 🚀"
+    echo ""
+    echo "This information has been saved to codespace-details.txt"
+    echo ""
+    echo "Joomla Admin Login:"
+    echo "  URL: Open the 'Ports' tab, find the 'Web Server' (443), and click the Globe icon. Then add /administrator"
+    echo "  Username: $ADMIN_USER"
+    echo "  Password: $ADMIN_PASS"
+    echo ""
+    echo "phpMyAdmin Login:"
+    echo "  URL: Open the 'Web Server' port and add /phpmyadmin"
+    echo "  Username: $DB_USER"
+    echo "  Password: $DB_PASS"
+    echo ""
+    echo "Cypress E2E Testing:"
+    echo "  Run interactive tests: npx cypress open"
+    echo "  Run headless tests:   npx cypress run"
+    echo ""
+    echo "Xdebug for PHP Debugging:"
+    echo "  Xdebug is pre-configured on port 9003. Use the 'Run and Debug' panel in VS Code and select 'Listen for Xdebug'."
+    echo "---"
+} | tee "$DETAILS_FILE"
diff --git a/.devcontainer/xdebug.ini b/.devcontainer/xdebug.ini
new file mode 100644
index 0000000000000..61b89fca18d38
--- /dev/null
+++ b/.devcontainer/xdebug.ini
@@ -0,0 +1,7 @@
+[xdebug]
+zend_extension=xdebug
+xdebug.mode=debug
+xdebug.log_level = 0
+xdebug.start_with_request=yes
+xdebug.client_port=9003
+xdebug.client_host=localhost