Which capability is supported by reusable workflows but NOT by composite actions?

Composite actions insert their steps into the job that called them; they cannot declare additional jobs or job-level needs. Reusable workflows are workflows triggered via workflow_call and may include a full multi-job graph, environments, and job-level controls. Both can define inputs and both are referenced with uses: at a ref (for reusable workflows the path points at a workflow file). Both can run shell steps (composite requires shell on run steps). Choose composite for reusable step sequences and setup logic; choose reusable workflows when you need standardized multi-job pipelines (build, test, deploy) shared across repositories. secrets: inherit is a reusable workflow calling feature, not a composite concept.