Theory

Updated

October 30, 2026

Theory: A Workflow is a Graph of Jobs Triggered by Git Events

Actions YAML in Git is both source and config. An event (push, PR, schedule) instantiates jobs, each a sequence of steps on a runner.

Invariants

  1. Jobs in a workflow may run in parallel unless needs says otherwise.
  2. The GITHUB_TOKEN is a short-lived credential scoped to the repo/job.
  3. Contexts (github, secrets, matrix) are the runtime environment.
event → workflow → jobs → steps → runner VM/container

What can break

  • Unpinned third-party actions on main.

How to read this chapter

Why Actions, anatomy, runtime, authoring/debug, build/validate.