AKS clusters with unsupported Windows node pools (WS2019 / Annual Channel) — migrate to Windows Server 2022/2025

What LeftSize checks

Find AKS clusters with Windows node pools on Windows Server 2019 or Windows Server Annual Channel (preview). Both are already unsupported.

Why it matters

Missed retirement and end-of-support dates turn into forced upgrades, outages or extended support charges at a moment you did not choose.

What you get in the GitHub issue

LeftSize runs this check from a scheduled GitHub Action with a read-only identity in your Azure account and opens one issue per scope, updated on every scan. The issue includes:

• The affected resources, grouped per subscription, resource group or account and region
• Background on why it was flagged and when it is a false positive
• Cost and operational impact of fixing it
• Alternative approaches and their trade-offs
• Step-by-step remediation with safety checks
• Ready-to-run fix scripts (CLI, PowerShell or Terraform where available)
• Snooze, ignore or report a finding with a comment on the issue

Official references

• https://learn.microsoft.com/en-us/azure/aks/windows-faq
• https://learn.microsoft.com/en-us/azure/aks/node-images
• https://learn.microsoft.com/en-us/azure/aks/upgrade-windows-os