9.1. What You've Built
Phase 1 established the execution model everything else refines: automation as reaction to events, jobs isolated on disposable runners, and the three granularities of reuse. If you can decompose an unfamiliar scenario into that chain, you can reason about questions covering features you've never used.
Phase 2 made you an author — triggers and their filters, workflow_dispatch and workflow_call interfaces, job graphs and conditionals, service containers, matrices, anchors, contexts and expressions, and the deliberate channels (outputs, artifacts, caches) that move data through ephemeral machines.
Phase 3 scaled all of that to an organization: governance through templates and policy tiers, runner fleets with groups and network controls, and the secret-scoping hierarchy whose real lesson is blast radius.
Phase 4 turned you into a reader — diagnosing from run metadata, Set up job, and step logs; expanding anchors and matrices mentally; locating evidence through the UI and API; and choosing correctly among starter, reusable, and composite reuse by binding time.
Phase 5 crossed to the producer side: the three action types and their trade-offs, the action.yml contract, immutable publishing, and the versioning discipline that consumers depend on.
Phase 6 tied it together — token scoping, script injection, OIDC, supply chain defenses, environment gates — and then made it fast and affordable.
