Argo CD ApplicationSet and Git Generator: When Does Pruning Delete Child Applications?

Direct answer

Pruning deletes a child Application when the ApplicationSet controller’s next successful reconciliation finds that the Git generator no longer emits the parameter set that created it. The controller matches child Applications by the argocd.argoproj.io/applicationset-name label and deletes the match unless spec.prune is explicitly false. It does not evaluate every intermediate commit; it reads the repository state at the configured ref, branch, tag, or commit during its periodic resync.

Confirmed facts versus likely explanation

Item	Status	Detail
Prune trigger	Confirmed	Missing generator output at the next successful reconciliation, for an ApplicationSet-owned child Application.
Per-commit pruning	Confirmed	Not supported; intermediate or high-frequency pushes are not individually observed.
Delay or approval gate	Confirmed	No native grace period, retention window, or manual approval; only spec.prune: false.
Temporarily fewer entries	Likely explanation	Next successful reconciliation prunes the now-missing child Applications; a failed Git read generally preserves the previous generation until the next successful run.
Orphaned Applications	Confirmed	With spec.prune: false, previously generated children remain and are not automatically re-adopted if the entry later reappears.

Steps for this case

1. Inspect the ApplicationSet manifest: kubectl get applicationset -n <namespace> <name> -o yaml and confirm spec.prune and spec.generators[].git.
2. Confirm the installed ApplicationSet controller version, because reconciliation timing and pruning defaults can vary by Argo CD release.
3. If you want to stop deletions immediately while investigating, set spec.prune: false on the ApplicationSet. Expect previously generated child Applications to remain orphaned.
4. To verify behavior safely, remove one watched file from the Git source on a test branch, wait for one controller reconciliation interval, and check whether the corresponding child Application is deleted.

Missing diagnostic detail

What is the installed Argo CD ApplicationSet controller version? This changes the expected reconciliation interval and may change default pruning behavior, so it affects whether the observed deletion timing is normal.

Verification

Review controller logs around the reconciliation window: kubectl logs -n argocd deployment/argocd-applicationset-controller --tail=100. Look for Git generator read errors and delete events for child Applications. If logs show a failed repository read, treat the previous generation as unchanged until the next successful run.

Assumption: this answer covers ApplicationSet-level pruning only. It does not cover Application sync-policy prune options, which are a separate mechanism.