This is indeed build time extraction. There is an "Extract app intents metadata" step in the build log. The way this works is that the Swift compiler outputs some information that it generates while compiling your code, which describes what types are available in your code, as well as type-level and some value-level information from your App Intents method implementations. This information is parsed by another tool which generates a metadata.appintents directory in your built product which contains files that describe your intents, and other information we need to know without running your app, such as information needed to render your intents in Shortcuts.