Point a stage at the resource that produces an artifact, and the controller finds the ExternalArtifact that producer publishes. This is the third source route, alongside the two direct ones — an ExternalArtifact (the default sourceRef.kind) or a Flux GitRepository/OCIRepository/Bucket — covered in stages and sources . Reach for it when an operator publishes an ExternalArtifact from a custom resource (for example JaaS rendering Jsonnet).

Referencing a producer

Set kind (and apiVersion) to a producer resource, and the controller resolves it to the ExternalArtifact that producer publishes — the one whose spec.sourceRef back-references the producer (matched on group, kind, and name). For example, a JaaS JsonnetSnippet renders Jsonnet and publishes an ExternalArtifact; reference the snippet and the controller follows the link:

spec:
  stages:
    - name: dashboards
      sourceRef:
        apiVersion: jaas.metio.wtf/v1
        kind: JsonnetSnippet
        name: grafana-dashboards

The controller also watches the common Flux source kinds (GitRepository, OCIRepository, Bucket) so a stage re-reconciles when an upstream source changes.

A producer can itself consume another producer first: a JaaS JsonnetSnippet can render from the artifact another snippet publishes. That chaining happens on the producer side — see chaining snippets . A stage references only the final producer and reads the ExternalArtifact it publishes.

Related projects

JOI, JaaS, and StageSet compose end to end:

• JOI publishes Jsonnet libraries as single-layer OCI images (usable both as image-volume mounts and as Flux OCIRepository sources).
• JaaS evaluates Jsonnet — optionally importing those JOI libraries — and publishes the rendered JSON as an ExternalArtifact.
• StageSet references the JsonnetSnippet (or its artifact) and rolls the result out in ordered, gated stages.

Each project is independently useful; a stage reads straight from a GitRepository, OCIRepository, or Bucket, or from any ExternalArtifact regardless of what produced it.