April 2026 monthly summary for microsoft/hcsshim focused on architectural improvements in the HCS integration. Delivered a refactor of the VM and Network controllers to encapsulate HCS document generation and VM options handling within the VM Controller, reducing leakage of VM options into the service layer. Updated the Network controller to include namespace and policy options in the New call, with Start remaining option-free to standardize startup across LCOW/WCow paths. This work enhances modularity, reliability, and maintainability of the runtime path, setting a solid foundation for future features and easier testing.

March 2026 (2026-03) highlights across microsoft/hcsshim focusing on stability, maintainability, and capability expansion. Deliverables span in-guest command execution, VM Sandbox V2 support, LCOW UVM HCS building, and targeted codebase refactors, complemented by parsing and concurrency fixes that improve reliability for production workloads.

February 2026 delivered core guest-operations capabilities, lifecycle visibility for Utility VMs, and Windows-ready shim modernization for microsoft/hcsshim, with a focus on reliability, cross-shim reuse, and developer velocity. Key outcomes include: (1) guest operations interfaces and refined cross-shim connection handling with configurable GCS GUID; (2) Utility VM lifecycle APIs (StartedTime/StoppedTime) and lifecycle-aware WaitSandbox with AcceptConnection relocation to vmmanager; (3) shim modernization with upstream containerd shim integration, Windows compatibility (build tags, logging pipes), remote events publisher, and optimized vmmem lookup via Windows API abstraction; (4) internal refactors to vmutils, centralized constants/logging, and reusable UVM reference parsing utilities. These changes improve observability, maintainability, and cross-platform consistency, enabling faster delivery of VM-related features and easier future shim integrations.

January 2026 (microsoft/hcsshim): Consolidated delivery of sandbox lifecycle, resource management, and registry migration with targeted cleanup to improve reliability and maintainability. Notable contributions include a new sandbox API and gRPC service, pod-level cgroup enforcement with LCOW CPU defaults, and alignment of image references to registry.k8s.io, accompanied by removing the obsolete remotevm path.

November 2025 Monthly Summary for containerd/containerd focusing on the Sandbox feature delivery and related quality improvements.