helm diff --three-way-merge does not detect manual changes on Custom Resources (CRDs)

[orco49]

We are seeing inconsistent behavior with helm diff upgrade --three-way-merge when detecting manual changes made directly in the Kubernetes cluster, specifically for Custom Resources (CRDs).

For built-in Kubernetes resources (e.g. Deployment), helm diff --three-way-merge correctly detects live changes made via kubectl edit/patch.
However, for CRDs (example below uses KEDA ScaledObject), manual changes in the cluster are not detected, even when the field is explicitly defined in the Helm chart.

What works ✅
For built-in resources (e.g. Deployment):

1.Deploy via Helm
2.Manually edit:
kubectl edit deployment my-app
change resources.limits.memory value

Run:
helm diff upgrade <release> <chart> --three-way-merge --dry-run

➡️ The manual change is detected and shown in the diff.

What does NOT work ❌
For CRDs (example: KEDA ScaledObject):

1. Deploy via Helm with spec.maxReplicaCount defined in the chart
2. Manually edit the ScaledObject:

kubectl patch scaledobject my-so \
  -n <ns> \
  --type=merge \
  -p '{"spec":{"maxReplicaCount":30}}'

Run:
helm diff upgrade <release> <chart> --three-way-merge --dry-run

➡️ No diff is shown, even though the live value differs from the chart.

Questions:

1. Is this a known limitation of helm-diff with CRDs?
2. Is --three-way-merge expected not to detect live drift for CRDs?
3. Are there plans or recommendations for supporting live drift detection on CRDs?