Update the Helm chart or Kubernetes manifest to reference the new image tag then commit the change and open a pull request is correct.

This is because ArgoCD follows the GitOps model and treats the Git repository as the source of truth. You deploy a new image by updating the desired state in Git, for example by changing the image tag in the Helm chart or Kubernetes manifest and then creating a pull request. When that change is merged ArgoCD will detect the updated manifest and sync the cluster according to its configured sync policy.

Rely on the ArgoCD operator to detect the new image and update the cluster automatically is incorrect because ArgoCD does not by default scan container registries and replace image tags. Detecting and updating images in registries requires an additional tool or an image updater component and is not the built in behavior of ArgoCD.

Push the updated image to Artifact Registry and configure a Cloud Build trigger to modify manifests in Git is incorrect because although you can automate manifest edits with a CI trigger this describes extra CI configuration and is not the immediate GitOps step. The essential requirement is that the manifest or chart in Git must change so ArgoCD can apply the new desired state.

Open the ArgoCD web UI and edit the application to change the image reference manually is incorrect because making manual edits in the ArgoCD UI changes cluster state without updating Git. That breaks the GitOps practice of using Git as the single source of truth and such UI edits will be overwritten on the next sync from the repository.

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