Theory

Updated

October 30, 2026

Theory: Reconciliation is Compare Desired to Actual, Forever

Argo CD’s Application is a pointer at Git (desired) plus a cluster (actual). The controller loop diffs and optionally syncs. Immutable infrastructure: replace, do not SSH-mutate.

Invariants

  1. Five-step loop: detect, compare, present, sync (if policy), record.
  2. Repo server renders manifests (Helm/Kustomize/plain) in a sandbox.
  3. Sync status and health are different questions.
Git  →  repo-server  →  desired manifests
cluster API  →  actual
controller: diff + sync policy

What can break

  • Editing live resources that auto-sync will revert.

How to read this chapter

History, reconciliation, loop, components, apps/projects, path to cluster, desired vs actual.