Helm, Kustomize and plain YAML sources

The repo server detects the source type and renders it: a folder of YAML, a Kustomize overlay, or a Helm chart with values files and parameters.

Argo CD never runs helm install. The repo server renders the source into plain manifests, and the controller applies them. It picks the tool by looking at the folder:

Folder contains	Rendered with
`kustomization.yaml`	Kustomize (`kustomize build`)
`Chart.yaml`	Helm (`helm template`)
Only `.yaml` / `.json`	Plain directory (add `directory.recurse: true` for subfolders)
A plugin config	A Config Management Plugin (sidecar)

Kustomize overlays per environment

apps/shop-api/
  base/            deployment.yaml  service.yaml  kustomization.yaml
  overlays/
    dev/           kustomization.yaml   # replicas 1, image tag 1.4.3
    prod/          kustomization.yaml   # replicas 3, image tag 1.4.2, HPA

# overlays/prod/kustomization.yaml
resources: [../../base]
images:
  - name: registry.example.com/shop-api
    newTag: "1.4.2"
replicas:
  - name: shop-api
    count: 3

Each environment is one Application pointing at its overlay path. You can also override a few things on the Application (spec.source.kustomize.images, namePrefix, commonLabels), but keeping them in the overlay keeps Git the single source of truth.

Helm charts

spec:
  source:
    repoURL: https://charts.example.com          # a Helm repo (or oci://registry.example.com/charts)
    chart: shop-api
    targetRevision: 2.3.1                        # chart version
    helm:
      releaseName: shop-api
      valueFiles: [values-prod.yaml]             # only for charts in Git
      valuesObject:
        replicaCount: 3
        image: { tag: "1.4.2" }

For a chart stored in Git, use repoURL + path and list valueFiles relative to the chart.
For a chart from a Helm or OCI registry, use chart + a pinned version.
Multiple sources (spec.sources) let you take the chart from a registry and the values file from your config repo, using a ref: source and $values/envs/prod/values.yaml.
helm ls shows nothing: Argo CD owns the objects, not Helm. Rollback through Git or Argo CD, not helm rollback.
Helm hooks are mapped to Argo CD hooks (next lessons), so most charts work unchanged.

Check before you commit

kustomize build apps/shop-api/overlays/prod | less
helm template shop-api charts/shop-api -f charts/shop-api/values-prod.yaml | less
argocd app manifests shop-api-prod          # what Argo CD itself rendered
argocd app create shop-api-prod ... --helm-set image.tag=1.4.2   # parameters from the CLI (avoid in GitOps)

Rule: parameters set with argocd app set --helm-set live only in the Application object. Prefer values files in Git; if you do use parameters, make sure the Application YAML itself is in Git.