Symptom

READY=False, REASON=ArtifactNotFound. Transient: the controller requeues in case the artifact appears.

Cause

A stage’s sourceRef resolves to no ExternalArtifact. Either:

• a direct sourceRef (kind: ExternalArtifact, the default) names an object that does not exist in the target namespace; or
• a producer sourceRef (e.g. kind: JsonnetSnippet) exists, but no ExternalArtifact carries a spec.sourceRef back-pointer to it yet — the producer has not created its artifact object.

Diagnosis

kubectl describe stageset <name> -n <namespace>     # Message names the missing ref
kubectl get externalartifact -n <namespace>

For a producer ref, confirm the producer object exists and that it is configured to publish an ExternalArtifact (not only serve over HTTP):

kubectl get <producer-kind> <name> -n <namespace> -o yaml

Remediation

• Fix a typo in sourceRef.name / sourceRef.namespace.
• For a direct ref, create (or wait for) the named ExternalArtifact.
• For a producer ref, ensure the producer actually publishes an artifact and that it lands in the same namespace as the StageSet (cross-namespace producer refs are gated by --no-cross-namespace-refs).

If the artifact exists but is not yet published, the reason is SourceNotReady; a spec/API resolution failure is ResolveFailed. See stages and sources.