Preprocess functions are the bridge between Drupal’s backend logic and Twig templates. While Twig is responsible for presentation, preprocess functions prepare and structure the data before it reaches the template layer.

Theme debugging in Drupal is the process of identifying how markup is generated, which templates are being used, how variables are passed to Twig, and why expected changes are not appearing on the frontend.

Today marks the beginning of my 90‑day journey into applied AI engineering as a Senior Drupal developer. The goal is not to become a data scientist, but to become an AI‑enabled backend engineer who can responsibly integrate LLMs into real production systems.

Twig is the foundation of Drupal’s frontend rendering layer. In Drupal 10 and 11, every piece of visible markup — from nodes and blocks to views and layouts — ultimately passes through Twig templates.

We now arrive at the final topic of Level 2 – Backend Development.

Throughout this series, we have built a complete backend architecture inside the weeklydrupal_demo module: