Kubernetes-sigs Agent Sandbox v1.0.0 removes v1alpha1 APIs and changes default behaviors

The Kubernetes-sigs Agent Sandbox project has released version v1.0.0, marking a significant update with several breaking changes and new features. According to the project's GitHub release notes, the core and extension APIs have transitioned to v1beta1, fully removing support for the legacy v1alpha1 APIs and associated conversion webhook infrastructure. This change improves performance by eliminating API server conversion round-trips, webhook latency, and potential failure modes such as certificate rotation issues and firewall blocks in private clusters. Additionally, controllers no longer write the `agents.x-k8s.io/pod-name` annotation to Sandbox resources, relying instead on the guaranteed equivalence between Sandbox names and backing Pod names. This adjustment reduces reconciliation latency and API server load under high demand.

Operators should carefully review their upgrade path, as direct upgrades from versions earlier than v0.5.0 are not supported. Existing clusters must first upgrade to v0.5.x, perform storage migration to rewrite resources to v1beta1, and verify stored versions before proceeding to v1.0.0. Skipping these steps will result in upgrade failures. Furthermore, any external scripts or monitoring tools relying on the deprecated `pod-name` annotation must be updated to use `.metadata.name` instead. The removal of webhook resources post-upgrade is also necessary to clean up orphaned configurations.

This release aligns with a broader pattern observed in Kubernetes projects where deprecated APIs and legacy infrastructure are phased out to streamline performance and reduce operational complexity. Operators should ensure compatibility with these changes to avoid disruptions during the upgrade process.