Long-form notes on the parts of Drupal you only meet when something is slow, broken, or newly possible, in chronological order.
Agents write PHP faster than anyone can review it, and reviewing means following calls. PHPlumb is a code navigation engine built for that loop. It is fast on 40,000-file projects, it follows types through Drupal's service container, and it stays silent when it is not sure.
Entity Adapter attaches domain-specific behaviour to entities, and to any other object, with a PHP attribute and an interface of your own. No bundle class, no entity class override, no helper functions in a .module file.
Drupal spends a request filling static caches and then throws the whole process away. Keep the process alive, in a Symfony Messenger worker or a FrankenPHP worker, and every one of those caches becomes a lie that outlives the work it was computed for.
WebProfiler now collects every call the AI module makes to a provider, with timings, tokens, guardrail verdicts and tool exchanges. Here is what it records and how it stays out of the AI module's way.