April 2026 monthly summary for buildkite/agent-stack-k8s: Key feature delivered this month focuses on improving workspace isolation for concurrent jobs running on shared volumes. Introduced a configurable per-pod subdirectory mechanism to apply a subPathExpr to every /workspace VolumeMount across all relevant containers (init containers, check containers, agent, checkout, and command containers). This enables per-pod subdirectories on a node's shared hostPath workspace, preventing collisions and clobbering when multiple jobs run in parallel, while preserving current behavior if the option is not set. Impact: enhanced concurrency, reliability, and performance for multi-job CI workloads on Kubernetes. The change supports per-node shared-cache patterns and reduces workspace contention, enabling more predictable builds and faster job throughput. Notes: canonical setup uses workspace-mount-sub-path-expr: $(POD_NAME) exposed via downward API, with tests covering both configured propagation and default no-subPath behavior. Overall, this quarter’s work demonstrates strong focus on isolation, scalability, and maintainability, with clear traceability to commits and configuration-driven behavior.